Great start. And what does your (or any) documentation of usbip says, how to go on?

I don’t use usbip, so I googled for ‘opkg usbip’ and got: [OpenWrt Wiki] USB over IP tunnel

You installed kmod-… This standing for something like ‘kernel module’.
Every of your operating systems has different ‘areas/layer/sections/…’. somewhere at the ring 0 is your hardware, roundabout ring 1 is ‘the kernel’ (the technical real operating system). Above are userland tools, the binaries and Programms you know, which you are working every day. A set of this tools is known as distribution.

And because the kernel needs to be more flexible today, where we have various hardware and don’t want to recompile for any possible set of hardware, there are modules, that can be loaded into the kernel, to access special hardware.

You installed the kernel module for a layer between IP (Net) and USB (xHCI) … But no userland tools to interact with this modules.

According to the link above, your solution is:

opkg install kmod-usb-ohci usbip-server usbip-client