Revert "Revert "arm64: hugetlb: partial revert of 66b3923a""

The use of the contiguous bit by our hugetlb implementation violates
the break-before-make requirements of the architecture and can lead to
silent data corruption or TLB conflict aborts. Once again, disable these
hugetlb sizes whilst it gets worked out.

This reverts commit ab2e1b89.

Conflicts:
	arch/arm64/mm/hugetlbpage.c

Signed-off-by: Will Deacon <will.deacon@arm.com>