power: fix the privilege of the reboot operation

power: fix the privilege of the reboot operation

Previously, the privilege of the reboot operation was
"http://tizen.org/privilege/power" since the method
is registered on the "org.tizen.system.deviced.power" interface.
But the device_power_reboot() document of capi-system-device
noticed that the operation requires "http://tizen.org/privilege/reboot"
privilege.

Now, the privilege of the reboot operation is changed
to "http://tizen.org/privilege/reboot" according to
the device_power_reboot(). For the change, the dbus method
interface is changed to "org.tizen.system.deviced.reboot".

Change-Id: I928fc35710f8713c74b84d0aa434fc60e084fc2c
Signed-off-by: taeyoung <ty317.kim@samsung.com>