dax: Remove an unused field in struct dax_operations

.dax_supported() was apparently removed by commit 7b0800d ("dax:
remove dax_capable") on 2021-11.

Remove the now unused function pointer from the struct dax_operations.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/56b92b722ca0a6fd1387c871a6ec01bcb9bd525e.1725203804.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

include/linux/dax.h

@@ -27,12 +27,6 @@ struct dax_operations {
 	 */
 	long (*direct_access)(struct dax_device *, pgoff_t, long,
 			enum dax_access_mode, void **, pfn_t *);
-	/*
-	 * Validate whether this device is usable as an fsdax backing
-	 * device.
-	 */
-	bool (*dax_supported)(struct dax_device *, struct block_device *, int,
-			sector_t, sector_t);
 	/* zero_page_range: required operation. Zero page range   */
 	int (*zero_page_range)(struct dax_device *, pgoff_t, size_t);
 	/*