rxrpc: Use irq-disabling spinlocks between app and I/O thread

Where a spinlock is used by both the application thread and the I/O thread,
use irq-disabling locking so that an interrupt taken on the app thread
doesn't also slow down the I/O thread.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>