clocksource/drivers/timer-tegra186: Fix watchdog self-pinging

clocksource/drivers/timer-tegra186: Fix watchdog self-pinging

This change removes watchdog self-pinging behavior.

The timer irq handler is triggered due to the 1st expiration,
the handler disables and enables watchdog but also implicitly
clears the expiration count so the count can only be 0 or 1.

Since this watchdog supports opened, configured, or pinged by
systemd, We remove this behavior or the watchdog may not bark
when systemd crashes since the 5th expiration never comes.

Signed-off-by: Pohsun Su <pohsuns@nvidia.com>
Signed-off-by: Robert Lin <robelin@nvidia.com>
Link: https://lore.kernel.org/r/20250507044311.3751033-3-robelin@nvidia.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>