sendfile: remove .sendfile from filesystems that use generic_file_sendfile()

They can use generic_file_splice_read() instead. Since sys_sendfile() now
prefers that, there should be no change in behaviour.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/ntfs/file.c

@@ -2276,7 +2276,7 @@ const struct file_operations ntfs_file_ops = {
 						    mounted filesystem. */
 	.mmap		= generic_file_mmap,	 /* Mmap file. */
 	.open		= ntfs_file_open,	 /* Open file. */
-	.sendfile	= generic_file_sendfile, /* Zero-copy data send with
+	.splice_read	= generic_file_splice_read /* Zero-copy data send with
 						    the data source being on
 						    the ntfs partition.  We do
 						    not need to care about the