rt2x00: Use lib->config_filter() during scheduled packet filter config

Now rt2x00lib handles the initial configure_filter() command, we can
directly call lib->config_filter() in scheduled context since the
called function will no longer check if anything has changed (which is
now handled in rt2x00lib as well).

This fixes a endless loop with USB drivers where the config_filter
command was scheduled time and time again without sending any command
to the device.

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