control: Support target_path option in configuration file

The target path containing the interface
xyz.openbmc_project.control.FanPwm or
xyz.openbmc_project.control.FanSpeed can be different between
phosphor-hwmon and dbus-sensor.

In phosphor-hwmon, it is "/xyz/openbmc_project/sensors/fan_tach/".
In dbus-sensor, it is "/xyz/openbmc_project/control/fanpwm/"

This commit supports making this path configurable via "target_path".
By default, it is "/xyz/openbmc_project/sensors/fan_tach/".

Signed-off-by: Chau Ly <chaul@amperecomputing.com>
Change-Id: Id799986ff69455b7c7054070ed2ab3b2e2500a6c
8 files changed