Synch to mcu-tool/mcuboot 2fa1190f

Synchronized up to:
https://github.com/mcu-tools/mcuboot/commit/2fa1190ff36ff8cbaf8eb76cad68386d3c668b66



- zephyr: fixed typo in watchdog support
- serial recovery: fixed build failure if CONFIG_BOOT_SERIAL_DETECT_PIN
has undefined value 

Merged using GH web GUI

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>