rt2x00: Align RT chipset definitions with vendor driver.

Only include definitions for RT chipsets that are also used inside the
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>