drm/i915/display: Enable MSA Ignore Timing PAR only when in not fixed_rr mode

MSA Ignore Timing PAR enable is set in the DP sink when we enable variable
refresh rate.

Currently for link training we depend on flipline to decide whether we
want to ignore the msa timings. With fixed refresh rate we will still
fill the flipline in all cases whether panel supports VRR or not.

Change the condition for link training to ignore the msa timings if
vrr.in_range.

v2: Add more documentation and a #TODO for readout of vrr.in_range.
(Ville)

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/20250311093751.1329043-9-ankit.k.nautiyal@intel.com