bus: arm-ccn: Fix node->XP config conversion

Events defined as watchpoints on nodes must have their config values
converted so that they apply to the respective node's XP. The
function setting new values was using wrong mask for the "port" field,
resulting in corrupted value. Fixed now.

Cc: stable@vger.kernel.org # 3.17+
Signed-off-by: Pawel Moll <pawel.moll@arm.com>