Print debug information on user faults for SIGBUS if user_debug = 16
in the kernel command line.

Reference: <1327333344-26340-1-git-send-email-javi.merino@arm.com>

Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>