powerpc/eeh: Drop taken reference to driver on eeh_rmv_device

powerpc/eeh: Drop taken reference to driver on eeh_rmv_device

Commit 9f58d944e90b4f02bfa51d6c62021b7934bdc5a8 ("powerpc/eeh: Use
partial hotplug for EEH unaware drivers") introduces eeh_rmv_device,
which may grab a reference to a driver, but not release it.

That prevents a driver from being removed after it has gone through EEH
recovery.

This patch drops the reference if it was taken.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Acked-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>