presence: Un-hardcode input device path

Allow a device path to be configured.

Change-Id: I2eabd71747b124eae96738d1332f58b96ece6dc9
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/presence/gpio.hpp b/presence/gpio.hpp
index e516e0f..978fdd9 100644
--- a/presence/gpio.hpp
+++ b/presence/gpio.hpp
@@ -41,9 +41,13 @@
          * @brief Construct a gpio sensor.
          *
          * @param[in] physDevice - The physical gpio device path.
+         * @param[in] device - The gpio-keys input device.
          * @param[in] physPin - The physical gpio pin number.
          */
-        Gpio(const std::string& physDevice, unsigned int physPin);
+        Gpio(
+                const std::string& physDevice,
+                const std::string& device,
+                unsigned int physPin);
 
         /**
          * @brief start