usbip: Fix uninitialized variable bug in vhci

The patch 03cd00d5: "usbip: vhci-hcd: Set the vhci structure up
to work" introduced a bug which uses a vairable without initialization
in error handling code. Fix it.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>