power: reset: linkstation-poweroff: add new device

This commit introduces support for NETGEAR ReadyNAS Duo v2.
This device use bit 4 of LED[2:0] Polarity Control Register to indicate
AC Power loss.

For more details about AC loss detection in NETGEAR ReadyNAS Duo v2,
please look at the file:
RND_5.3.13_WW.src/u-boot/board/mv_feroceon/mv_hal/usibootup/usibootup.c
from Netgear GPL sources.

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

power: reset: linkstation-poweroff: prepare for new devices

This commit prepare driver for another device support.

New power_off_cfg structure describes two most important things: name of
mdio bus and pointer to register setting function. It allow to add new
device with different mdio bus node and other phy register config.

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

power: reset: linkstation-poweroff: add missing put_device()

The of_mdio_find_bus() takes a reference to the underlying device
structure, we should release that reference using a put_device() call.

Signed-off-by: Daniel González Cabanelas <dgcbueu@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

power: reset: add driver for LinkStation power off

Some Buffalo LinkStations perform the power off operation, at restart
time, depending on the state of an output pin (LED2/INTn) at the ethernet
PHY. This pin is also used to wake the machine when a WoL packet is
received by the PHY.

The driver is required by the Buffalo LinkStation LS421DE (ARM MVEBU),
and other models. Without it, the board remains forever halted if a
power off command is executed, unless the PSU is disconnected and
connected again.

Add the driver to provide the power off function and also make the WoL
feature to be available.

Signed-off-by: Daniel González Cabanelas <dgcbueu@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>