drm/amd/display: Drop unnecessary header file

powerplay implement hwmgr_function table for all supported asics in
order to conceal the asic's detail infomation. so no need to include
the smu10_hwmgr.h.

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