watchdog: apple: Actually flush writes after requesting watchdog restart

Although there is an existing code comment about flushing the writes,
writes were not actually being flushed.

Actually flush the writes by changing readl_relaxed() to readl().

Fixes: 4ed224ae ("watchdog: Add Apple SoC watchdog driver")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Nick Chan <towinchenmi@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20241001170018.20139-2-towinchenmi@gmail.com


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