watchdog: db8500_wdt: Rename driver

This driver is named after the ambition to support more SoCs than
the DB8500. Those were never produced, so cut down the scope and
rename the driver accordingly. Since the Kconfig for the watchdog
defaults to y this will still be built by default.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210922230947.1864357-2-linus.walleij@linaro.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>