device-dax: Tell kbuild DEV_DAX_PMEM depends on DEV_DAX

ERROR: "devm_create_dev_dax" [drivers/dax/dax_pmem.ko] undefined!
ERROR: "alloc_dax_region" [drivers/dax/dax_pmem.ko] undefined!
ERROR: "dax_region_put" [drivers/dax/dax_pmem.ko] undefined!
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/dax/Kconfig

@@ -19,7 +19,7 @@ config DEV_DAX
 
 config DEV_DAX_PMEM
 	tristate "PMEM DAX: direct access to persistent memory"
-	depends on LIBNVDIMM && NVDIMM_DAX
+	depends on LIBNVDIMM && NVDIMM_DAX && DEV_DAX
 	default DEV_DAX
 	help
 	  Support raw access to persistent memory.  Note that this