Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:5474:5: warning: no previous prototype for ‘vega10_hwmgr_init’ [-Wmissing-prototypes]
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:551: warning: Function parameter or member 'hwmgr' not described in 'vega10_get_evv_voltages'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:609: warning: Function parameter or member 'hwmgr' not described in 'vega10_patch_with_vdd_leakage'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:609: warning: Function parameter or member 'voltage' not described in 'vega10_patch_with_vdd_leakage'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:609: warning: Function parameter or member 'leakage_table' not described in 'vega10_patch_with_vdd_leakage'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:637: warning: Function parameter or member 'hwmgr' not described in 'vega10_patch_lookup_table_with_leakage'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:637: warning: Function parameter or member 'lookup_table' not described in 'vega10_patch_lookup_table_with_leakage'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:637: warning: Function parameter or member 'leakage_table' not described in 'vega10_patch_lookup_table_with_leakage'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1013: warning: Function parameter or member 'hwmgr' not described in 'vega10_trim_voltage_table'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1013: warning: Function parameter or member 'vol_table' not described in 'vega10_trim_voltage_table'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1160: warning: Function parameter or member 'hwmgr' not described in 'vega10_construct_voltage_tables'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1558: warning: Function parameter or member 'hwmgr' not described in 'vega10_populate_single_gfx_level'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1558: warning: Function parameter or member 'gfx_clock' not described in 'vega10_populate_single_gfx_level'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1558: warning: Function parameter or member 'current_gfxclk_level' not described in 'vega10_populate_single_gfx_level'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1558: warning: Function parameter or member 'acg_freq' not described in 'vega10_populate_single_gfx_level'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1613: warning: Cannot understand  * @brief Populates single SMC SOCCLK structure using the provided clock.
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1667: warning: Function parameter or member 'hwmgr' not described in 'vega10_populate_all_graphic_levels'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1750: warning: Cannot understand  * @brief Populates single SMC GFXCLK structure using the provided clock.
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:1811: warning: Cannot understand  * @brief Populates all SMC MCLK levels' structure based on the trimmed allowed dpm memory clock states.
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:2496: warning: Function parameter or member 'hwmgr' not described in 'vega10_init_smc_table'
 drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:2867: warning: Cannot understand  * @brief Tell SMC to enabled the supported DPMs.

Cc: Evan Quan <evan.quan@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>