OMAP2PLUS: WDT: Fix: Disable WDT after reset during init

Inorder to avoid any assumptions from bootloader, the watchdog
timer module is reset during init. This enables the watchdog
timer.

Therefore, it is required to disable WDT after it is reset
during init. Otherwise the system would reboot as per the default
watchdog timer registers settings.

Later, when the watchdog driver is loaded, the watchdog timer settings
is adjusted as per the default timer_margin set in the driver and the
driver would supports the normal operations supported by OMAP watchdog
timer.

Signed-off-by: Charulatha V <charu@ti.com>
Reported-by: Kevin Hilman <khilman@deeprootsystems.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>