usbip: Fix USB device hang due to wrong enabling of scatter-gather

The previous USB3 SuperSpeed enabling patches mistakenly enabled
URB scatter-gather chaining, which is actually not supported by
the VHCI HCD. This patch fixes that.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=197867
Fixes: 03cd00d5

 ("usbip: vhci-hcd: Set the vhci structure up to work")
Reported-by: Juan Zea <juan.zea@qindel.com>
Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>