watchdog: ftwdt010: need to reset watchdog in ftwdt010_wdt_start()

ftwdt010_wdt_start() has to call ftwdt010_wdt_reset() after setting-up
the timeout in the same fashion ftwdt010_wdt_expire_now() does it.

Without this patch the "wdt start <ms>" command does not actually start
the watchdog timer until the "wdt reset" command is executed.

Signed-off-by: Sergei Antonov <saproj@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>