rt2x00: rt2800: add antenna diversity for RT5370G

rt2x00: rt2800: add antenna diversity for RT5370G

RT5370G has hardware RX antenna diversity like RT5390R.
Based on DPO_RT5572_LinuxSTA_2.6.1.3_20121022.tar.bz2 manufacturer driver:
https://d86o2zu8ugzlg.cloudfront.net/mediatek-craft/drivers/DPO_RT5572_LinuxSTA_2.6.1.3_20121022.tar.bz2

Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Helmut Schaa <helmut.schaa@googlemail.com>
Cc: Gertjan van Wingerde <gwingerde@gmail.com>
Cc: Jakub Kicinski <jakub.kicinski@netronome.com>
Cc: wireless newbie <wnewbie72@gmail.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: linux wireless ml <linux-wireless@vger.kernel.org>
Signed-off-by: Xose Vazquez Perez <xose.vazquez@gmail.com>
Acked-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>