staging: rtl8723bs: Remove rtw_btcoex_IsBtDisabled()

Remove function rtw_btcoex_IsBtDisabled as it does nothing except call
hal_btcoex_IsBtDisabled.
Modify call sites accordingly.
Issue found wth Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Link: https://lore.kernel.org/r/20190701091817.12759-6-nishkadg.linux@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>