clocksource: Reduce the default clocksource_watchdog() retries to 2

[ Upstream commit 1a562067 ]

With the previous patch, there is an extra watchdog read in each retry.
Now the total number of clocksource reads is increased to 4 per iteration.
In order to avoid increasing the clock skew check overhead, the default
maximum number of retries is reduced from 3 to 2 to maintain the same 12
clocksource reads in the worst case.

Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Stable-dep-of: f2655ac2 ("clocksource: Fix brown-bag boolean thinko in cs_watchdog_read()")
Signed-off-by: Sasha Levin <sashal@kernel.org>