drm/i915/xehpsdv: set min page-size to 64K

Conditionally allocate LMEM with 64K granularity, since 4K page support
for LMEM will be dropped on some platforms when using the PPGTT.

v2:
  updated commit msg [Thomas]

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Thomas Hellstrom <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211208154854.28037-1-ramalingam.c@intel.com