staging: rtl8723bs: remove unsed hal_btcoex_SetDBG() function

remove unused hal_btcoex_SetDBG() function definition and
prototype.

Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Fabio Aiuto <fabioaiuto83@gmail.com>
Link: https://lore.kernel.org/r/4f8aa4e4312777aff1aea621d26c00e81754025a.1619794331.git.fabioaiuto83@gmail.com


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