rtlwifi: btcoex: rename ex_halbtc*ant to ex_btc*ant

rtlwifi: btcoex: rename ex_halbtc*ant to ex_btc*ant

These external functions are for BT-coexistence, so remove the "hal"
prefix for consistancy.

Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Ping-Ke Shih <pkshih@realtek.com>
Cc: Birming Chiu <birming@realtek.com>
Cc: Shaofu <shaofu@realtek.com>
Cc: Steven Ting <steventing@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>