scripts/dtc: Update to upstream version v1.4.5-6-gc1e55a5513e9

Pickup the fix for handling unresolved phandles in overlays.

This adds the following commits from upstream:

c1e55a5513e9 checks: fix handling of unresolved phandles for dts plugins
f8872e29ce06 tests: Avoid 64-bit arithmetic in assembler
48c91c08bcfa libfdt: add stringlist functions to linker script

Signed-off-by: Rob Herring <robh@kernel.org>
[ Linux commit: e45fe7f788dd1395befe5639149ad8dacfbd94ab ]
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/scripts/dtc/checks.c b/scripts/dtc/checks.c
index 08a3a29..e661384 100644
--- a/scripts/dtc/checks.c
+++ b/scripts/dtc/checks.c
@@ -988,6 +988,10 @@
 		 * entries when each index position has a specific definition.
 		 */
 		if (phandle == 0 || phandle == -1) {
+			/* Give up if this is an overlay with external references */
+			if (dti->dtsflags & DTSF_PLUGIN)
+				break;
+
 			cellsize = 0;
 			continue;
 		}
@@ -1176,6 +1180,11 @@
 		prop = get_property(parent, "interrupt-parent");
 		if (prop) {
 			phandle = propval_cell(prop);
+			/* Give up if this is an overlay with external references */
+			if ((phandle == 0 || phandle == -1) &&
+			    (dti->dtsflags & DTSF_PLUGIN))
+					return;
+
 			irq_node = get_node_by_phandle(root, phandle);
 			if (!irq_node) {
 				FAIL(c, dti, "Bad interrupt-parent phandle for %s",