drm/i915/xe3lpd: Add condition for EDP to powerdown P2.PG

Add condition for P2.PG power down value.

v2: change subject line to better match patch condition

Bspec: 74494
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241018200311.67324-8-matthew.s.atwood@intel.com