dax: stop using bdevname

Just use the %pg format specifier instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/20210826135510.6293-3-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>