drm/amd/pp: remove polaris10_smc/smumgr split.

move functions in polaris_smc.c to
polaris10_smumgr.c and make all functions in
polaris10_smumgr.c static.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>