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

 drivers/gpu/drm/amd/amdgpu/../display/dc/bios/bios_parser2.c:501: warning: Function parameter or member 'dcb' not described in 'bios_parser_get_gpio_pin_info'
 drivers/gpu/drm/amd/amdgpu/../display/dc/bios/bios_parser2.c:501: warning: Function parameter or member 'gpio_id' not described in 'bios_parser_get_gpio_pin_info'
 drivers/gpu/drm/amd/amdgpu/../display/dc/bios/bios_parser2.c:501: warning: Function parameter or member 'info' not described in 'bios_parser_get_gpio_pin_info'
 drivers/gpu/drm/amd/amdgpu/../display/dc/bios/bios_parser2.c:815: warning: Function parameter or member 'dcb' not described in 'bios_parser_get_spread_spectrum_info'
 drivers/gpu/drm/amd/amdgpu/../display/dc/bios/bios_parser2.c:815: warning: Function parameter or member 'signal' not described in 'bios_parser_get_spread_spectrum_info'
 drivers/gpu/drm/amd/amdgpu/../display/dc/bios/bios_parser2.c:815: warning: Function parameter or member 'index' not described in 'bios_parser_get_spread_spectrum_info'
 drivers/gpu/drm/amd/amdgpu/../display/dc/bios/bios_parser2.c:815: warning: Function parameter or member 'ss_info' not described in 'bios_parser_get_spread_spectrum_info'
 drivers/gpu/drm/amd/amdgpu/../display/dc/bios/bios_parser2.c:1210: warning: Function parameter or member 'dcb' not described in 'bios_parser_set_scratch_critical_state'
 drivers/gpu/drm/amd/amdgpu/../display/dc/bios/bios_parser2.c:1210: warning: Function parameter or member 'state' not described in 'bios_parser_set_scratch_critical_state'

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@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>