drm/i915/dp: Add from_crtc_state to copy color blobs

No functional changes here, just adds a from_crtc_state
as a prep for bigjoiner

v2:
* More prep with intel_atomic_state (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201113155656.17630-2-manasi.d.navare@intel.com