hw/watchdog: Allwinner WDT emulation for system reset

hw/watchdog: Allwinner WDT emulation for system reset

This patch adds basic support for Allwinner WDT.
Both sun4i and sun6i variants are supported.
However, interrupt generation is not supported, so WDT can be used only to trigger system reset.

Signed-off-by: Strahinja Jankovic <strahinja.p.jankovic@gmail.com>
Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Tested-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Message-id: 20230326202256.22980-2-strahinja.p.jankovic@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>