watchdog: omap_wdt: Fix WDT target reset when booted from emmc

watchdog: omap_wdt: Fix WDT target reset when booted from emmc

AM335X based beaglebone black target gets reset by DM converted watchdog
if booted from emmc around 60sec. Fixed this by moving driver's private struct
variable initialization at different places in the driver to driver's probe.
Tested on Beaglebone Black.

Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Fixes: 7659ea32 ("watchdog: omap_wdt: Convert watchdog driver to use DT and DM")
Reported-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Suniel Mahesh <sunil.m@techveda.org>
Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>