drm/i915/vrr: Use set_context_latency instead of intel_vrr_real_vblank_delay()

drm/i915/vrr: Use set_context_latency instead of intel_vrr_real_vblank_delay()

The helper intel_vrr_real_vblank_delay() was added to account for the
SCL lines for TGL where we do not have the TRANS_SET_CONTEXT_LATENCY.

Now, since we already are tracking the SCL with new member
`set_context_latency` use it directly instead of the helper.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://lore.kernel.org/r/20250924141542.3122126-4-ankit.k.nautiyal@intel.com