[packages] usbip: remove usbip-server dependency on usbip-client

Signed-off-by: Nuno Goncalves <nunojpg@gmail.com>

git-svn-id: svn://svn.openwrt.org/openwrt/packages@40865 3c298f89-4303-0410-b956-a3cf2f4a3e73