Have the Target class manage the file descriptor

The sysfs file descriptor will now stay open from first
use until the Target class is destroyed.

Change-Id: Ib9803a527115cc75ecc9a5351d1e748ccd54a993
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/filedescriptor.hpp b/filedescriptor.hpp
index b03d314..2a4c6d0 100644
--- a/filedescriptor.hpp
+++ b/filedescriptor.hpp
@@ -5,7 +5,7 @@
 
 namespace openpower
 {
-namespace p9_util
+namespace util
 {
 
 /**
@@ -40,7 +40,7 @@
         /**
          * The method to access the file descriptor value
          */
-        inline int operator()() const
+        inline auto get() const
         {
             return fd;
         }