pm8001: fix a memory leak in nvmd_resp

Instead of copying information to fw_control_context free it.

The task is forgotten thus also the reference to fw_control_context
and the completion thread takes the info from virt_ptr again.

Signed-off-by: Tomas Henzl <thenzl@redhat.com>
Acked-by: Suresh Thiagarajan <Suresh.Thiagarajan@pmcs.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>