arm64: reorganise PAGE_/PROT_ macros

Make these macros available to assembly code, so they can be re-used by the
PIE initialisation code.

This involves adding some extra macros, prepended with _ that are the raw
values not `pgprot` values.

A dummy value for PTE_MAYBE_NG is also provided, for use in assembly.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20230606145859.697944-14-joey.gouly@arm.com


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>