powerpc/powernv/ioda: Release opencapi device

With hotplug, an opencapi device can now go away. It needs to be
released, mostly to clean up its PE state. We were previously not
defining any device callback. We can reuse the standard PCI release
callback, it does a bit too much for an opencapi device, but it's
harmless, and only needs minor tuning.

Also separate the undo of the PELT-V code in a separate function, it
is not needed for NPU devices and it improves a bit the readability of
the code.

Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191121134918.7155-5-fbarrat@linux.ibm.com