xive_esb_rw() is the common routine used for memory accesses on ESB
page. Use it for triggers also.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20211006210546.641102-1-clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>