ARM: orion5x: Fix GPIO enable bits for MPP9

Commit 554cdaef ('ARM: orion5x: Refactor
mpp code to use common orion platform mpp.') seems to have accidentally
inverted the GPIO valid bits for MPP9 (only).  For the mv2120 platform
which uses MPP9 as a GPIO LED device, this results in the error:

[   12.711476] leds-gpio: probe of leds-gpio failed with error -22

Reported-by: Henry von Tresckow <hvontres@gmail.com>
References: http://bugs.debian.org/667446


Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: stable@vger.kernel.org [v3.0+]
Tested-by: Hans Henry von Tresckow <hvontres@gmail.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>