power: reset: use restart_notifier mechanism for msm-poweroff

This change replaces use of arm_pm_restart with recently introduced
reset mechanism in Linux kernel called restart_notifier.

Choosing priority 128, which is default priority, as according to
documentation, this mechanism is sufficient to restart the entire system.

Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Josh Cartwright <joshc@codeaurora.org>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: linux-pm@vger.kernel.org

Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Pramod Gurav <pramod.gurav@smartplayin.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>