x86/spinlock: Leftover conversion ACCESS_ONCE->READ_ONCE

commit 78bff1c8 ("x86/ticketlock: Fix spin_unlock_wait() livelock")
introduced two additional ACCESS_ONCE cases in x86 spinlock.h.
Lets change those as well.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>