feat(libfdt): upgrade libfdt source files

Update the libfdt source files to the upstream commit e37c256 [1].

[1] https://github.com/dgibson/dtc/commit/e37c256

Change-Id: I00e29b467ff6f8c094f68245232a7cedeaa14aef
Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>
diff --git a/lib/libfdt/fdt_addresses.c b/lib/libfdt/fdt_addresses.c
index 9a82cd0..c40ba09 100644
--- a/lib/libfdt/fdt_addresses.c
+++ b/lib/libfdt/fdt_addresses.c
@@ -73,7 +73,7 @@
 	/* check validity of address */
 	prop = data;
 	if (addr_cells == 1) {
-		if ((addr > UINT32_MAX) || ((UINT32_MAX + 1 - addr) < size))
+		if ((addr > UINT32_MAX) || (((uint64_t) UINT32_MAX + 1 - addr) < size))
 			return -FDT_ERR_BADVALUE;
 
 		fdt32_st(prop, (uint32_t)addr);