rt2x00: Add rt3071 support in rt2800 register initialization.

Add RT3071 specific register initializations to rt2x00, based on the latest
Ralink rt3070 vendor driver.

With this patch my RT3071 based devices start showing a sign of life.

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>