net: fec: fix the potential memory leak in fec_enet_init()

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

net: fec: fix the potential memory leak in fec_enet_init()

If the memory allocated for cbd_base is failed, it should

free the memory allocated for the queues, otherwise it causes

memory leak.

And if the memory allocated for the queues is failed, it can

return error directly.