staging: rtl8723bs: simplify function selecting channel group

staging: rtl8723bs: simplify function selecting channel group

simplify function Hal_GetChnlGroup8723B(). It returns
an unused and unnecessary bool value telling which
band the device works on. Since we work only on
2.4Ghz band and the useful return value is the
second function argument we convert the return type to
void.

remove 5Ghz dead code either (for channel > 14).

Signed-off-by: Fabio Aiuto <fabioaiuto83@gmail.com>
Link: https://lore.kernel.org/r/a5536788004c44fe819c0eab0d19504824af46cd.1626874164.git.fabioaiuto83@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>