staging: vt6655: Remove unused byRFType in rf.c

Remove byRFType that support 5GHz band.
Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/640bdbc0ff135c6a63d6764fd81a8bb24d5053dd.1646512837.git.philipp.g.hortmann@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>