rtlwifi: btcoex: add settings before the hardware is ready

When the hardware is turned on and in the initialization stage, the PTA
circuit is unstable. Hence we need to force some hardware settings to
make sure the PTA circuit work correctly, otherwise it may affect the
user's experience.

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>