Add the missing `MODULE_LICENSE()` tag to the `rzv2h_wdt` driver, which
resolves the following modpost error when built as a module:

    ERROR: modpost: missing MODULE_LICENSE() in drivers/watchdog/rzv2h_wdt.o

Fixes: f6febd0a ("watchdog: Add Watchdog Timer driver for RZ/V2H(P)")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240911132031.544479-1-prabhakar.mahadev-lad.rj@bp.renesas.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>