drm/i915/hotplug: Add comment for XE_LPD+ SHPD_FILTER_CNT value

Add the reason for having SHPD_FILTER_CNT value for XE_LPD+ and
above as 250us instead of 500us.

--v2
-Update commit message [Matt]

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240923031007.1058072-4-suraj.kandpal@intel.com