arm64: mm: Declare support for large anonymous folios

For the unhinted case, when THP is not permitted for the vma, don't
allow anything bigger than 64K. This means we don't waste too much
memory. Additionally, for 4K pages this is the contpte size, and for
16K, this is (usually) the HPA size when the uarch feature is
implemented. For the hinted case, when THP is permitted for the vma,
allow the contpte size for all page size configurations; 64K for 4K, 2M
for 16K and 2M for 64K.

Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>