Add I2C OCC support for P8 systems

P8 system uses I2C OCC and it uses different driver for occ-hwmon.
Add `--enable-i2c-occ` configure option to enable the support.

It searches i2c device names in sysfs to get all occ-hwmon devices and
use the i2c device name to bind/unbind the driver.

The occ control object path for I2C OCC hwmon becomes something like
/org/open_power/control/3_0050, where 3_0050 is the i2c address.

Change-Id: I8b9d8d4429c563528dc88fb2679b265c53d7a2d5
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/occ_device.hpp b/occ_device.hpp
index 6538597..a2b4e85 100644
--- a/occ_device.hpp
+++ b/occ_device.hpp
@@ -5,6 +5,8 @@
 #include "occ_events.hpp"
 #include "occ_errors.hpp"
 #include "config.h"
+
+
 namespace open_power
 {
 namespace occ
@@ -34,7 +36,11 @@
         Device(EventPtr& event,
                const std::string& name,
                std::function<void()> callBack = nullptr) :
+#ifdef I2C_OCC
+            config(name),
+#else
             config(name + '-' + "dev0"),
+#endif
             errorFile(fs::path(config) / "occ_error"),
             error(event, errorFile, callBack)
         {