staging: rtl8723bs: clean driver from unused RF paths

staging: rtl8723bs: clean driver from unused RF paths

rtl8723bs support only two rf paths (A and B), remove all
the others (C, D, BC, ...) as they are unused. Keep
just one enum selecting rf path, remove unused macro
indicating max rf path number, add an item in rf_path
enum for this pourpose.

Signed-off-by: Fabio Aiuto <fabioaiuto83@gmail.com>
Link: https://lore.kernel.org/r/23060c85ab9aa468c9c021378f0dc8a8f887a578.1628329348.git.fabioaiuto83@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>