FruDevice: Don't scan Mux bus if root is in blacklist

This checks to see if the root of a bus is in the blacklist
and avoids scanning it if that is true.

Tested: Used prints to verify that mux busses were skipped

Change-Id: I3bb5c3ffb349d4a09ac8fe67a7b33defe1250c20
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/src/FruDevice.cpp b/src/FruDevice.cpp
index 42ca311..4d93fc1 100644
--- a/src/FruDevice.cpp
+++ b/src/FruDevice.cpp
@@ -650,12 +650,19 @@
         {
             busnum.erase(0, lastDash + 1);
         }
+
         auto bus = std::stoi(busnum);
         if (busBlacklist.find(bus) != busBlacklist.end())
         {
             continue; // skip previously failed busses
         }
 
+        int rootBus = getRootBus(bus);
+        if (busBlacklist.find(rootBus) != busBlacklist.end())
+        {
+            continue;
+        }
+
         auto file = open(i2cBus.c_str(), O_RDWR);
         if (file < 0)
         {