Replace the custom page table allocation implementation with the
standard allocator.

The driver loses the ability to map 64kB chunkgs using the PTE
contiguous hint, hence the removal of the SZ_64K page size from the
IOMMU page sizes bitmap.
Signed-off-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>