binman: Allow entries to expand after packing

Add support for detecting entries that change size after they have already
been packed, and re-running packing when it happens.

This removes the limitation that entry size cannot change after
PackEntries() is called.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/test/121_entry_expand.dts b/tools/binman/test/121_entry_expand.dts
new file mode 100644
index 0000000..ebb7816
--- /dev/null
+++ b/tools/binman/test/121_entry_expand.dts
@@ -0,0 +1,20 @@
+/dts-v1/;
+
+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	binman {
+		_testing {
+			bad-update-contents;
+		};
+
+		u-boot {
+		};
+
+		_testing2 {
+			type = "_testing";
+			bad-update-contents;
+		};
+	};
+};