rt2x00: rt2800lib: turn on secondary PAs/LNAs for 3T/3R devices

The secondary PAs/LNAs are turned on only for 2T/2R
devices, however these are used for 3T/3R devices as
well. Always turn those on if the device uses more
than one tx/rx chains.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Acked-by: Stanislaw Gruszka <stf_xl@wp.pl>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>