rtlwifi: btcoex: 23b 2ant: new fw use h2c to control GNT_BT

Earlier versions of the FW did not support h2c to set GNT_BT, but later
versions have that capability. Hence we check the FW version and decide
whether to use h2c or just write to the register.

Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Pkshih <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>