Add overlay logic to Entity Manager

Generate overlays and fixup symbols to map virtual i2c
busses to muxes. Also scan muxes in order as they seem
to get confused if we scan them out of order.

Change-Id: Iec3ed49fca22db8537e4474d9d95cab2da574aef
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/configurations/1Ux16 Riser.json b/configurations/1Ux16 Riser.json
index 533985e..1669436 100644
--- a/configurations/1Ux16 Riser.json
+++ b/configurations/1Ux16 Riser.json
@@ -37,7 +37,7 @@
                 "address": "0x72",
                 "bus": "$bus",
                 "name": "Riser 1 Mux",
-                "type": "SMBusMux"
+                "type": "PCA9543Mux"
             },
             {
                 "address": "$address",
@@ -87,7 +87,7 @@
                 "address": "0x73",
                 "bus": "$bus",
                 "name": "Riser 2 Mux",
-                "type": "SMBusMux"
+                "type": "PCA9543Mux"
             },
             {
                 "address": "$address",