uio_hv_generic: Fix another memory leak in error handling paths

In the Linux kernel, the following vulnerability has been resolved:

uio_hv_generic: Fix another memory leak in error handling paths

Memory allocated by 'vmbus_alloc_ring()' at the beginning of the probe

function is never freed in the error handling path.

Add the missing 'vmbus_free_ring()' call.

Note that it is already freed in the .remove function.