drm/i915/fbc: Pass around FBC instance instead of crtc

drm/i915/fbc: Pass around FBC instance instead of crtc

Pass the FBC instance instead of the crtc to a bunch of places.

We also adjust intel_fbc_post_update() to do the
intel_fbc_get_reg_params() things instead of doing it from the lower
level function (which also gets called for front buffer tracking).
Nothing in there will change during front buffer updates.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211124113652.22090-8-ville.syrjala@linux.intel.com
Reviewed-by: Mika Kahola <mika.kahola@intel.com>