lib: utils/reset: add priority to gpio reset

Make gpio_system_reset_check return priority instead of just true/false.

Make default 128 priority for reset/shutdown.

Tested-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Tested-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: Nikita Shubin <n.shubin@yadro.com>