Makefile: Update minimum dtc version to 1.4.3

With support for overlays and calling the -@ flag to dtc we need to have
at least 1.4.3 available now.

Cc: Simon Glass <sjg@chromium.org>
Reported-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/Makefile b/Makefile
index 8250b34..e058e98 100644
--- a/Makefile
+++ b/Makefile
@@ -1448,8 +1448,8 @@
 		@$(call SYSTEM_MAP,$<) > $@
 
 checkdtc:
-	@if test $(call dtc-version) -lt 0104; then \
-		echo '*** Your dtc is too old, please upgrade to dtc 1.4 or newer'; \
+	@if test $(call dtc-version) -lt 010403; then \
+		echo '*** Your dtc is too old, please upgrade to dtc 1.4.3 or newer'; \
 		false; \
 	fi