pseq: Add named GPIO properties

Add the new named GPIO properties from the JSON config file to the
power sequencer device class hierarchy.

New JSON GPIO properties:
* power_control_gpio_name
* power_good_gpio_name

Power sequencer device class hierarchy:
* PowerSequencerDevice   (power_sequencer_device.*)
  * StandardDevice       (standard_device.*)
    * PMBusDriverDevice  (pmbus_driver_device.*)
      * UCD90xDevice     (ucd90x_device.*)
        * UCD90160Device (ucd90160_device.*)
        * UCD90320Device (ucd90320_device.*)

Tested:
* Ran automated tests. All ran successfully.

Change-Id: Idcccee89eb09cb7d135f45aeb4f6dfe8299adf43
Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
diff --git a/phosphor-power-sequencer/src/power_sequencer_device.hpp b/phosphor-power-sequencer/src/power_sequencer_device.hpp
index b7907c0..7597595 100644
--- a/phosphor-power-sequencer/src/power_sequencer_device.hpp
+++ b/phosphor-power-sequencer/src/power_sequencer_device.hpp
@@ -66,6 +66,21 @@
     virtual uint16_t getAddress() const = 0;
 
     /**
+     * Returns the name of the GPIO that turns this device on and off.
+     *
+     * @return GPIO name
+     */
+    virtual const std::string& getPowerControlGPIOName() const = 0;
+
+    /**
+     * Returns the name of the GPIO that reads the power good signal from this
+     * device.
+     *
+     * @return GPIO name
+     */
+    virtual const std::string& getPowerGoodGPIOName() const = 0;
+
+    /**
      * Returns the voltage rails that are enabled and monitored by this device.
      *
      * @return voltage rails