physical: Avoid unreachable statement in driveLED()

This also slightly improves the branch coverage statistics

Change-Id: I27d5168994831789a8f8dafeecc843242a7e406a
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/physical.cpp b/physical.cpp
index 77d3d4f..ae9ff1c 100644
--- a/physical.cpp
+++ b/physical.cpp
@@ -16,6 +16,7 @@
 
 #include "physical.hpp"
 
+#include <cassert>
 #include <iostream>
 #include <string>
 namespace phosphor
@@ -77,16 +78,13 @@
         return;
     }
 
-    if (request == Action::Blink)
-    {
-        return blinkOperation();
-    }
-
     if (request == Action::On || request == Action::Off)
     {
         return stableStateOperation(request);
     }
-    return;
+
+    assert(request == Action::Blink);
+    blinkOperation();
 }
 
 void Physical::stableStateOperation(Action action)