drm/i915/vrr: Avoid reading vrr.enable based on fixed_rr check

drm/i915/vrr: Avoid reading vrr.enable based on fixed_rr check

Currently, vrr.enable is intended only for variable refresh rate timings.
At this point, we do not set fixed refresh rate timings, but the GOP can,
which creates a problem during the readback of vrr.enable.

The GOP enables the VRR timing generator with fixed timings, while the
driver only recognizes the VRR timing generator as enabled with
variable timings. This discrepancy causes an issue due to the
fixed refresh rate check during readback. Since the VRR timing generator
is enabled and we do not support fixed timings, the readback should set
vrr.enable so that the driver can disable the VRR timing generator.
However, the current check does not allow this.

Therefore, remove the fixed refresh rate check during readback.

Fixes: 27217f9d1856 ("drm/i915/vrr: Track vrr.enable only for variable timing")
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250322044345.3827137-3-ankit.k.nautiyal@intel.com