1340: Add I2S for f4 r=Dirbaio a=xoviat
This is only for f4, but it puts us equal to or ahead of the standard rust hal.
1474: stm32: Fix watchdog timeout computation r=Dirbaio a=rmja
Co-authored-by: xoviat <xoviat@users.noreply.github.com>
Co-authored-by: Rasmus Melchior Jacobsen <rmja@laesoe.org>