PM: hibernate: Don't ignore return from set_memory_ro()

set_memory_ro() and set_memory_rw() can fail, leaving memory
unprotected.

Take the returned value into account and abort in case of
failure.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>