arm64: hibernate: Support DEBUG_PAGEALLOC

arm64: hibernate: Support DEBUG_PAGEALLOC

DEBUG_PAGEALLOC removes the valid bit of page table entries to prevent
any access to unallocated memory. Hibernate uses this as a hint that those
pages don't need to be saved/restored. This patch adds the
kernel_page_present() function it uses.

hibernate.c copies the resume kernel's linear map for use during restore.
Add _copy_pte() to fill-in the holes made by DEBUG_PAGEALLOC in the resume
kernel, so we can restore data the original kernel had at these addresses.

Finally, DEBUG_PAGEALLOC means the linear-map alias of KERNEL_START to
KERNEL_END may have holes in it, so we can't lazily clean this whole
area to the PoC. Only clean the new mmuoff region, and the kernel/kvm
idmaps.

This reverts commit da24eb1f3f9e2c7b75c5f8c40d8e48e2c4789596.

Change-Id: I862226802c9c726590c89e3d9e8062ed680309f3
Reported-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Git-Commit: 5ebe3a44cc744d11cb60d8438106a9322b7c04dc
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Arun KS <arunks@codeaurora.org>