watchdog: aspeed: fix 64-bit division

watchdog: aspeed: fix 64-bit division

On 32-bit architectures, the new calculation causes a build failure:

ld.lld-21: error: undefined symbol: __aeabi_uldivmod

Since neither value is ever larger than a register, cast both
sides into a uintptr_t.

Fixes: 5c03f9f4d362 ("watchdog: aspeed: Update bootstatus handling")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20250314160248.502324-1-arnd@kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>