mfd: tps65910: Set PWR_OFF bit during driver probe

The PWR_OFF bit needs to be set in order to power off properly, without
hanging PMIC. This bit needs to be set early in order to allow thermal
protection of NVIDIA Terga SoCs to power off hardware properly, otherwise
a battery re-plug may be needed on some devices to recover after the hang.

Cc: <stable@vger.kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Svyatoslav Ryhel <clamor95@gmail.com> # ASUS TF201
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211124190104.23554-1-digetx@gmail.com