arm64: Fix 5-level paging support in kexec/hibernate trampoline

arm64: Fix 5-level paging support in kexec/hibernate trampoline

Add the missing code to allocate P4D level page tables when cloning the
the kernel page tables. This fixes a crash that may be observed when
attempting to resume from hibernation on an LPA2 capable system with 4k
pages, which therefore uses 5 levels of paging.

Presumably, kexec is equally affected.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250110175145.785702-2-ardb+git@google.com
Signed-off-by: Will Deacon <will@kernel.org>