rt2x00: Align GPIO register definitions with the datasheets.

Ensure that all active GPIO pins are included in the GPIO register
definitions, nothing more and nothing less.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Ivo Van Doorn <ivdoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>