octeon_ep: fix potential memory leak in octep_device_setup()

When occur unsupported_dev and mbox init errors, it did not free oct->conf
and iounmap() oct->mmio[i].hw_addr. That would trigger memory leak problem.
Add kfree() for oct->conf and iounmap() for oct->mmio[i].hw_addr under
unsupported_dev and mbox init errors to fix the problem.

Fixes: 862cd659

 ("octeon_ep: Add driver framework and device initialization")
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>