hwc\overlay: Remove support for foreground override

Remove support for overriding a layer's z to set it up for foreground.
This is unused and can be achieved using pipes staged at required
z-orders.

Change-Id: Ia4688beed770c44c20d201a2dc5687252e002981
diff --git a/liboverlay/overlayUtils.cpp b/liboverlay/overlayUtils.cpp
index 86e9349..f9ee326 100644
--- a/liboverlay/overlayUtils.cpp
+++ b/liboverlay/overlayUtils.cpp
@@ -309,9 +309,9 @@
         const mdp_overlay& ov) {
     char str[256] = {'\0'};
     snprintf(str, 256,
-            "%s id=%d z=%d fg=%d alpha=%d mask=%d flags=0x%x H.Deci=%d,"
+            "%s id=%d z=%d alpha=%d mask=%d flags=0x%x H.Deci=%d,"
             "V.Deci=%d\n",
-            prefix, ov.id, ov.z_order, ov.is_fg, ov.alpha,
+            prefix, ov.id, ov.z_order, ov.alpha,
             ov.transp_mask, ov.flags, ov.horz_deci, ov.vert_deci);
     strlcat(buf, str, len);
     getDump(buf, len, "\tsrc", ov.src);