drm/xe: move the lmem verification code into a separate function

drm/xe: move the lmem verification code into a separate function

If lmem (VRAM) is not fully initialized, the punit will power down
the GT, which will prevent register access from the driver side.
That code moved into a corresponding function (xe_verify_lmem_ready)
to make the code clearer.

Signed-off-by: Koby Elbaz <kelbaz@habana.ai>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20231029175326.626745-1-kelbaz@habana.ai
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>