ARM: sa1111: change devid to be a bitmask

Change the sa1111 device id to be a bitmask.  This allows us to
specify the actual device, while allowing a single driver to bind
to both PS2 devices.

Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>