watchdog: omap_wdt: Fix WDT timeout configuration

The timeout parameter of omap3_wdt_start() is in miliseconds, while
GET_WLDR_VAL() expects parameter in seconds. Fix this so the WDT
driver is actually usable.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Sam Protsenko <semen.protsenko@linaro.org>
Cc: Suniel Mahesh <sunil.m@techveda.org>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>