intel_wait_for_vblank() goes through a pipe to crtc lookup, while in
most cases we already have the crtc available. Avoid the extra lookups
by adding an intel_crtc based helper.

v2:
- Add intel_crtc_wait_for_next_vblank() helper (Ville)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/90cfbd8c3e79a742b0ee9e3ae75493acb0785dbb.1638366969.git.jani.nikula@intel.com