watchdog: Add Watchdog Timer driver for RZ/G2L

Add Watchdog Timer driver for RZ/G2L SoC.

WDT IP block supports normal watchdog timer function and reset
request function due to CPU parity error.

This driver currently supports normal watchdog timer function
and later will add support for reset request function due to
CPU parity error.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20211130195357.18626-3-biju.das.jz@bp.renesas.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>