scripts: pre-submit: Ensure changelog captures API updates

I think most people have fallen short of this ideal at some point, so
add an automated check.

Change-Id: Ic7d2da4d97d49d7e5f43bc341b7e13381b8176e5
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
diff --git a/scripts/changelog.awk b/scripts/changelog.awk
new file mode 100644
index 0000000..e1644e6
--- /dev/null
+++ b/scripts/changelog.awk
@@ -0,0 +1,4 @@
+BEGIN { cl = 0; api = 0; }
+/^CHANGELOG.md$/ { cl=1 }
+/^include[/]libpldm/ { api=1 }
+END { exit !(cl || !api); }