fdt: Fix alignment issue when reading 64-bits properties from fdt

The FDT specification [0] gives a requirement of aligning properties on
32-bits. Make sure that the compiler is aware of this constraint when
accessing 64-bits properties.

[0]: https://github.com/devicetree-org/devicetree-specification/blob/master/source/flattened-format.rst

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/core/ofnode.c b/drivers/core/ofnode.c
index 297f0a0..8f0eab2 100644
--- a/drivers/core/ofnode.c
+++ b/drivers/core/ofnode.c
@@ -57,7 +57,7 @@
 
 int ofnode_read_u64(ofnode node, const char *propname, u64 *outp)
 {
-	const fdt64_t *cell;
+	const unaligned_fdt64_t *cell;
 	int len;
 
 	assert(ofnode_valid(node));