watchdog: orion: Add Armada 375/380 SoC support

This commit adds support for the Armada 375 and Armada 380 SoCs.

This SoC variant has a second RSTOUT register, in addition to the already
existent, which is shared with the system-controller. To handle this RSTOUT,
we introduce a new MMIO register 'rstout_mask' to be required on
'armada-{375,380}-watchdog' new compatible string.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Tested-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>