watchdog: tegra: revamp timeout calculation and usage

watchdog: tegra: revamp timeout calculation and usage

 - update calculation of timeout for TIMER_PTV,
 - update watchdog ping to first disable timer, update timeut value
   and then restart the timer.
 - init watchdog timeout using watchdog_init_timeout
 - program default trigger period in watchdog configuration regiter

Bug 200314562

Change-Id: Iec9e5a94c995653e5a3c653eccfa23a0877ae2e9
Signed-off-by: Shreshtha SAHU <ssahu@nvidia.com>
Reviewed-on: https://git-master/r/1515195
GVS: Gerrit_Virtual_Submit
Reviewed-by: Bibek Basu <bbasu@nvidia.com>
Tested-by: Bibek Basu <bbasu@nvidia.com>