staging: rtl8723bs: remove some 5 GHz code

Chips that use this driver are 2.4 GHz only. Remove some code that is
executed only for 5 GHz (channel > 14) . This addresses the following
TODO item:

- find and remove any code for other chips that is left over

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Reviewed-by: Hans de Goede <hansg@kernel.org>
Link: https://lore.kernel.org/r/20250615123859.41922-1-straube.linux@gmail.com


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