dpaa2_mc: Check for error the first time bus_generic_detach is called

[jhb]

Summary

This removes the need for the second call.

[dsl]

sys/dev/dpaa2/dpaa2_mc.c

286

In case of an error returned by any device_detach() all of the de-allocation below will be skipped. I'd rather log this error instead.

[jhb]

sys/dev/dpaa2/dpaa2_mc.c

286

But you can't just keep going. device_delete_children() is going to fail as well if bus_generic_detach() fails. That means you will still be attached, but will have your state partially destroyed, and child drivers can still call into your driver that now has mostly destroyed state and probably cause a panic. You have to stop if child drivers fail to detach.