regulators: Add configure support to System class

Implemented the configure() method in the System class.  This method
configures the regulator devices in all chassis in the system.

Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: Ie78aeb2b44bcb60da74f641743af34911cc13dd6
diff --git a/phosphor-regulators/src/system.hpp b/phosphor-regulators/src/system.hpp
index b0346ac..16e55b4 100644
--- a/phosphor-regulators/src/system.hpp
+++ b/phosphor-regulators/src/system.hpp
@@ -60,6 +60,14 @@
     }
 
     /**
+     * Configure the regulator devices in the system.
+     *
+     * This method should be called during the boot before regulators are
+     * enabled.
+     */
+    void configure();
+
+    /**
      * Returns the chassis in the system.
      *
      * @return chassis