staging: rtl8723bs: remove function rtw_get_ch_setting_union

because this function is not used.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Nam Cao <namcaov@gmail.com>
Link: https://lore.kernel.org/r/c8c5b0c78ee9a4cd8304efeff22b51049c75a3f2.1660916523.git.namcaov@gmail.com


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