drm/amd/display: change several dcn201 variables storage-class-specifier to static

smatch reports these similar problems in dcn201
drivers/gpu/drm/amd/amdgpu/../display/dc/clk_mgr/dcn201/dcn201_clk_mgr.c:165:22:
warning: symbol 'dcn201_funcs' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_resource.c:77:30:
warning: symbol 'dcn201_ip' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_resource.c:139:37:
warning: symbol 'dcn201_soc' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn201/dcn201_mpc.c:79:24:
warning: symbol 'dcn201_mpc_funcs' was not declared. Should it be static?

All of these are only used in their definition file, so they should be static

Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: add cyan_skillfish display support

[Why]
add display related cyan_skillfish files in.

makefile controlled by CONFIG_DRM_AMD_DC_DCN201 flag.

v2: squash in clang fixes from Harry, Nathan
v3: squash in missing CONFIG_DRM_AMD_DC check (Alex)

Signed-off-by: Charlene Liu <charlene.liu@amd.com>
Signed-off-by: Zhan Liu <zhan.liu@amd.com>
Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Acked-by: Jun Lei <jun.lei@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>