drm/i915/gtt: add xehpsdv_ppgtt_insert_entry

If this is LMEM then we get a 32 entry PT, with each PTE pointing to
some 64K block of memory, otherwise it's just the usual 512 entry PT.
This very much assumes the caller knows what they are doing.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220218184752.7524-11-ramalingam.c@intel.com