fs : Fix warning using plain integer as NULL

Sparse static analysis tools generate a warning with this message
"Using plain integer as NULL pointer". In this case this warning is
being shown because we are trying to initialize  pointer to NULL using
integer value 0.
Signed-off-by: Abhinav Singh <singhabhinav9051571833@gmail.com>
Link: https://lore.kernel.org/r/20231108044550.1006555-1-singhabhinav9051571833@gmail.comReviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/dax.c

@@ -1128,7 +1128,7 @@ static int dax_iomap_copy_around(loff_t pos, uint64_t length, size_t align_size,
 	/* zero the edges if srcmap is a HOLE or IOMAP_UNWRITTEN */
 	bool zero_edge = srcmap->flags & IOMAP_F_SHARED ||
 			 srcmap->type == IOMAP_UNWRITTEN;
-	void *saddr = 0;
+	void *saddr = NULL;
 	int ret = 0;
 
 	if (!zero_edge) {

fs/direct-io.c

@@ -1114,7 +1114,7 @@ ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 	loff_t offset = iocb->ki_pos;
 	const loff_t end = offset + count;
 	struct dio *dio;
-	struct dio_submit sdio = { 0, };
+	struct dio_submit sdio = { NULL, };
 	struct buffer_head map_bh = { 0, };
 	struct blk_plug plug;
 	unsigned long align = offset | iov_iter_alignment(iter);