power: reset: add LTC2952 poweroff driver

This adds a driver for the LTC2952, an external power control chip,
which signals the OS to shut down. Additionally this driver lets the
kernel power down the board.

Signed-off-by: René Moll <rene.moll@xsens.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

diff --cc drivers/power/reset/Kconfig
Simple merge

diff --cc drivers/power/reset/Makefile
Simple merge

diff --cc drivers/power/reset/ltc2952-poweroff.c
Simple merge