drm/xe/xe3p_lpg: Add missing indirect ring state feature flag

drm/xe/xe3p_lpg: Add missing indirect ring state feature flag

Even though commit 8fcb7dfb8bbf ("drm/xe/xe3p_lpg: Add support for
graphics IP 35.10") mentions that the support for Indirect Ring State
exists for Xe3p_LPG, it missed actually setting the feature flag in
graphics_xe3p_lpg.  Fix that by adding the missing member.

Fixes: 8fcb7dfb8bbf ("drm/xe/xe3p_lpg: Add support for graphics IP 35.10")
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patch.msgid.link/20260401-xe3p_lpg-indirect-ring-state-v1-1-0e4b5edf6898@intel.com
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>