drm/vblank: Introduce drm_crtc_vblank_crtc()

Make life easier by providing a function that hands
out the correct drm_vblank_crtc for a given a drm_crtc.

Also abstract the lower level internals of the vblank
code in a similar fashion.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240408190611.24914-1-ville.syrjala@linux.intel.com


Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>