rndis_wlan: fix initialization order for workqueue&workers

rndis_wext_link_change() might be called from rndis_command() at
initialization stage and priv->workqueue/priv->work have not been
initialized yet. This causes invalid opcode at rndis_wext_bind on
some brands of bcm4320.

Fix by initializing workqueue/workers in rndis_wext_bind() before
rndis_command is used.

This bug has existed since 2.6.25, reported at:
	http://bugzilla.kernel.org/show_bug.cgi?id=12794



Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>