The device mapper DAX support is all hanging off a block device and thus
can't be used with device dax.  Make it depend on CONFIG_FS_DAX instead
of CONFIG_DAX_DRIVER.  This also means that bdev_dax_pgoff only needs to
be built under CONFIG_FS_DAX now.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NMike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20211129102203.2243509-3-hch@lst.deSigned-off-by: NDan Williams <dan.j.williams@intel.com>