Staging: w35und: remove unused code from wbsoft_configure_filter()

We don't initialize hardware multicast filter in the driver nor do we know how
to do that. Therefore, remove some code that isn't actually used from
wbsoft_configure_filter().

Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>