staging: rtl8723bs: Remove rtw_btcoex_SetManualControl()

Remove function rtw_btcoex_SetManualControl as all it does is call
hal_btcoex_SetManualControl.
Modify call sites accordingly.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>