This patch allows support for 3 levels of page tables with 64KB page
configuration allowing 48-bit VA space. The pgd is no longer a full
PAGE_SIZE (PTRS_PER_PGD is 64) and (swapper|idmap)_pg_dir are not fully
populated (pgd_alloc falls back to kzalloc).
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Jungseok Lee <jungseoklee85@gmail.com>