iomap: mark the iomap argument to iomap_read_inline_data const

iomap_read_inline_data never modifies the passed in iomap, so mark
it const.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/iomap/buffered-io.c

@@ -206,7 +206,7 @@ struct iomap_readpage_ctx {
 };
 
 static int iomap_read_inline_data(struct inode *inode, struct page *page,
-		struct iomap *iomap)
+		const struct iomap *iomap)
 {
 	size_t size = i_size_read(inode) - iomap->offset;
 	size_t poff = offset_in_page(iomap->offset);