staging: rtl8723bs: remove hal_btcoex_GetDBG() function

remove unused hal_btcoex_GetDBG() 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/8b06dc12a65ef15f3e67bd32d097dc4db3f78586.1619794331.git.fabioaiuto83@gmail.com


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