arm64: hibernate: add PUD_SECT_RDONLY

There is PMD_SECT_RDONLY that is used in pud_* function which is confusing.

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Acked-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>