octeon_ep: fix potential memory leak in octep_device_setup()

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