rt2x00: Update rt2800 register definitions towards latest definitions.

Definitions taken from the latest rt2860 / rt2870 / rt3070 / rt3090 Ralink
vendor drivers.

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>