rt2x00: Fix rt2800lib RF chip programming selection.

Mirror the legacy Ralink driver with respect to rt2800 RF register
programming. Execute rt2800_config_channel_rt3x for all RF2020,
RF3020, RF3021 & RF3022 chipsets when operating on RT3070 devices.

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>