board: ge: bx50v3: Enable hardware watchdog

Enable the hardware watchdog on bx50v3 to cause it to reset in the event
the board hangs.

Configure GPIO_9 pin as WDOG1_B so that a watchdog timeout results in a
full system reset.

The watchdog is used and reconfigured by systemd approximately 1.7 seconds
into boot. Adding a few seconds for U-Boot and a few more seconds as a
safety margin.

Note that the PCIe controller is _not_ put back into a safe state prior
to board reset.  This is a problem if board reset is implemented as CPU
reset.

Signed-off-by: Ian Ray <ian.ray@ge.com>
Signed-off-by: Martyn Welch <martyn.welch@collabora.co.uk>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>