drm/amd/display: Add DC config flag for Raven2 (v2)

Add DRM_AMD_DC_DCN1_01 config flag for Raven2

v2: Make DC select DRM_AMD_DC_DCN1_01 (Alex)

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>