release-notes: Support P9 branch variable names

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/openpower/scripts/release-notes b/openpower/scripts/release-notes
index 402c88d..eb32d5c 100755
--- a/openpower/scripts/release-notes
+++ b/openpower/scripts/release-notes
@@ -77,11 +77,22 @@
         print "Old $1:$3\n";
         $old_level->{$1} = $3;
     }
+    if ($line =~ m/-([^[:space:]]*)_VERSION_BRANCH_MASTER([[:space:]]*\?*=[[:space:]]*)(.*)/)
+    {
+        print "Old $1:$3\n";
+        $old_level->{$1} = $3;
+    }
     if ($line =~ m/\+([^[:space:]]*)_VERSION([[:space:]]*\?*=[[:space:]]*)(.*)/)
     {
         print "New $1:$3\n";
         $new_level->{$1} = $3;
     }
+    if ($line =~ m/\+([^[:space:]]*)_VERSION_BRANCH_MASTER([[:space:]]*\?*=[[:space:]]*)(.*)/)
+    {
+        print "New $1:$3\n";
+        $new_level->{$1} = $3;
+    }
+
     if ($line =~ m/-[[:space:]]*default[[:space:]]*"([^[:space:]]*)"[[:space:]]*if[[:space:]]BR2_([^[:space:]]*)_LATEST_VERSION/)
     {
         print "Old $2:$1\n";