staging: rtl8723bs: Remove function rtw_btcoex_SetDBG()

staging: rtl8723bs: Remove function rtw_btcoex_SetDBG()

Remove function rtw_btcoex_SetDBG as all it does is call
hal_btcoex_setDBG.
Modify call sites accordingly.
Include the header file for hal_btcoex in the file that now calls
hal_btcoex_SetDBG instead of rtw_btcoex_SetDBG.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Link: https://lore.kernel.org/r/20190702070132.6997-6-nishkadg.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>