Refactor: rename namespace witherspoon to phosphor

This repo now becomes phosphor-power, rename namespace witherspoon to
phosphor to make it generic.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: Icb9f8a7c33065add99f2bf42ed55745a28fa0424
diff --git a/device.hpp b/device.hpp
index 2513506..7acd132 100644
--- a/device.hpp
+++ b/device.hpp
@@ -3,7 +3,7 @@
 #include <memory>
 #include <string>
 
-namespace witherspoon
+namespace phosphor
 {
 namespace power
 {
@@ -82,4 +82,4 @@
 };
 
 } // namespace power
-} // namespace witherspoon
+} // namespace phosphor