usb: usbip:checkpatch; fix bare use of unsigned

This patch fixes the following checkpatch warning for usbip files
WARNING: Prefer 'unsigned int' to bare use of 'unsigned'

Signed-off-by: Jai Krishna <rjk1024@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>