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/power-sequencer/main.cpp b/power-sequencer/main.cpp
index 3e1ca52..aa9b772 100644
--- a/power-sequencer/main.cpp
+++ b/power-sequencer/main.cpp
@@ -23,7 +23,7 @@
 #include <phosphor-logging/log.hpp>
 #include <sdeventplus/event.hpp>
 
-using namespace witherspoon::power;
+using namespace phosphor::power;
 using namespace phosphor::logging;
 
 int main(int argc, char** argv)