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

 In file included from drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:54:
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:537:3: note: in expansion of macro ‘MI_DCE8_MASK_SH_LIST’
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:537:3: note: in expansion of macro ‘MI_DCE8_MASK_SH_LIST’
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:542:3: note: in expansion of macro ‘MI_DCE8_MASK_SH_LIST’
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:542:3: note: in expansion of macro ‘MI_DCE8_MASK_SH_LIST’
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:547:2: note: in expansion of macro ‘DCE10_AUX_MASK_SH_LIST’
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:547:2: note: in expansion of macro ‘DCE10_AUX_MASK_SH_LIST’
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:551:2: note: in expansion of macro ‘DCE10_AUX_MASK_SH_LIST’
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:551:2: note: in expansion of macro ‘DCE10_AUX_MASK_SH_LIST’
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:889:16: warning: no previous prototype for ‘dce100_add_stream_to_ctx’ [-Wmissing-prototypes]
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:916:16: warning: no previous prototype for ‘dce100_validate_plane’ [-Wmissing-prototypes]
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:925:24: warning: no previous prototype for ‘dce100_find_first_free_match_stream_enc_for_link’ [-Wmissing-prototypes]
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce100/dce100_resource.c:1156:23: warning: no previous prototype for ‘dce100_create_resource_pool’ [-Wmissing-prototypes]

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: Anthony Koo <Anthony.Koo@amd.com>
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>