dax: remove CONFIG_DAX_DRIVER

CONFIG_DAX_DRIVER only selects CONFIG_DAX now, so remove it.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/20211129102203.2243509-4-hch@lst.deSigned-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/dax/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
-config DAX_DRIVER
-	select DAX
-	bool
-
 menuconfig DAX
 	tristate "DAX: direct access to differentiated memory"
 	select SRCU

drivers/nvdimm/Kconfig

@@ -22,7 +22,7 @@ if LIBNVDIMM
 config BLK_DEV_PMEM
 	tristate "PMEM: Persistent memory block device support"
 	default LIBNVDIMM
-	select DAX_DRIVER
+	select DAX
 	select ND_BTT if BTT
 	select ND_PFN if NVDIMM_PFN
 	help

drivers/s390/block/Kconfig

@@ -5,7 +5,7 @@ comment "S/390 block device drivers"
 config DCSSBLK
 	def_tristate m
 	select FS_DAX_LIMITED
-	select DAX_DRIVER
+	select DAX
 	prompt "DCSSBLK support"
 	depends on S390 && BLOCK
 	help

fs/fuse/Kconfig

@@ -45,7 +45,7 @@ config FUSE_DAX
 	select INTERVAL_TREE
 	depends on VIRTIO_FS
 	depends on FS_DAX
-	depends on DAX_DRIVER
+	depends on DAX
 	help
 	  This allows bypassing guest page cache and allows mapping host page
 	  cache directly in guest address space.