"cat /dev/mem" may cause kernel Oops for boards with PHYS_OFFSET != 0
because character device is mapped to addresses starting from zero
and there is no protection against such situation.
Patch just add this.
Signed-off-by: Alexandre Rusev <arusev@ru.mvista.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>