The rp2040 watchdog does not actually reset anything by default. The
psm_hw->wdsel field must be programmed to actually get a reset on a
watchdog failure. Program that field so the watchdog is usable.
Also, disable the watchdog before attempting a reboot into the
bootloader. Otherwise the machine may just reboot a second time due
to a missed watchdog event in the bootloader.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>