drivers: hwinfo: stm32: Deal with iwdgX and wwdgX instances

On some STM32 series (H7, MP1), iwdg and wwdg have multiple instances.
Due to current driver implementation, these wdg instances were not
checked in the function.

Fixes #53002

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>