nvme: return errors for hwmon init

Initializing the nvme hwmon retrieves a log from the controller. If the
controller is broken, we need to return the appropriate error so that
subsequent initialization doesn't attempt to continue.

Reported-by: Tong Zhang <ztong0001@gmail.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>