[PATCH] orinoco: fix setting transmit key only

When determining whether there's a key to set or not, orinoco should be
looking at the key length, not the key data.  Otherwise confusion reigns
when trying to set TX key only, passing in zero-length key, but non-NULL
pointer.  Key length takes precedence over non-NULL key data.

Signed-off-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>