[WATCHDOG] add SBC-FITPC2 watchdog driver

Add support for watchdog found on SBC-FITPC2 board.

Signed-off-by: Denis Turischev <denis@compulab.co.il>
Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>