staging: vt6656: Remove unused rf_type in card.c

Remove rf_type that supports 5GHz band.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/e768dbb116e79349aa083747729213d2d1ca7af9.1646935331.git.philipp.g.hortmann@gmail.com


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