drm/i915: Make vrr_{enabling,disabling}() usable outside intel_display.c

drm/i915: Make vrr_{enabling,disabling}() usable outside intel_display.c

Give vrr_enabling() and vrr_disabling() slightly fancier names, and
pass in the whole atomic state so that they'll be easier to use.
We'll need to call at least the disabling part from the DSB code
soon enough (so that we can do vblank evasions/etc. correctly on
the DSB).

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240624191032.27333-3-ville.syrjala@linux.intel.com
Reviewed-by: Animesh Manna <animesh.manna@intel.com>