kho: verify deserialization status and fix FDT alignment access

kho: verify deserialization status and fix FDT alignment access

During boot, kho_restore_folio() relies on the memory map having been
successfully deserialized.  If deserialization fails or no map is present,
attempting to restore the FDT folio is unsafe.

Update kho_mem_deserialize() to return a boolean indicating success.  Use
this return value in kho_memory_init() to disable KHO if deserialization
fails.  Also, the incoming FDT folio is never used, there is no reason to
restore it.

Additionally, use get_unaligned() to retrieve the memory map pointer from
the FDT.  FDT properties are not guaranteed to be naturally aligned, and
accessing a 64-bit value via a pointer that is only 32-bit aligned can
cause faults.

Link: https://lkml.kernel.org/r/20251114190002.3311679-6-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baoquan He <bhe@redhat.com>
Cc: Coiby Xu <coxu@redhat.com>
Cc: Dave Vasilevsky <dave@vasilevsky.ca>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Kees Cook <kees@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>