drm/xe/xe2: Track VA bits independently of max page table level

Starting with Xe2, a 5-level page table is always used, regardless of
the actual virtual address range supported by the platform.  The two
values need to be tracked separately in the device descriptor since Xe2
platforms only have a 48 bit virtual address range.

Bspec: 59505, 65637, 70817
Cc: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>