rt2x00: Fix channel configuration for RF3052

We missed a check for RF3052 in the config_channel
configuration function. As a result the channel is not
properly configured for RF3052 devices. This also
requires rt2800_config_channel_rf3xxx to support 5GHz
channels, so we must apply the TXPOWER_A_TO_DEV and
TXPOWER_G_TO_DEV conversions during rt2800_config_channel()

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Acked-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>