drm/xe/device: Convert wait for lmem init into an assert

drm/xe/device: Convert wait for lmem init into an assert

Prior to lmem init check, driver is waiting for the pcode uncore_init
status. uncore_init status will be flagged after the complete boot and
initialization of the SoC by the pcode. uncore_init confirms that lmem
init and mmio unblock has been already completed.
It makes no sense to check for lmem init after the pcode uncore_init
check. So change the wait for lmem init check into an assert which
confirms lmem init is set.

Signed-off-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patch.msgid.link/20251219145024.2955946-2-balasubramani.vivekanandan@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>