rt2x00: Invert scheduled packet_filter check

Invert the check for scheduling the packet_filter configuration.
When DRIVER_REQUIRE_SCHEDULED is not set we should immediately
configure the the filter.

This fixes the 'infinite calls to rt2x00mc_configure_filter'
bug reported by Bas Hulsken.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>