rtlwifi: add definition radio_mask for RF and maximum bandwidth

Add rf mask definition (BIT 0, BIT 1, BIT 2, ...) that is different from
rf path definition (0, 1, 2, ...), and then combinations of rf path are
possible.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>