power: reset: Add restart functionality for STiH41x platforms

This driver adds the restart functionality for STiH415 and STiH416
platforms from STMicroelectronics.  This driver registers an
arm_pm_restart function to reset the platform.

Signed-off-by: Christophe Kerello <christophe.kerello@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Sebastian Reichel <sre@kernel.org>