rcu: Permit start_poll_synchronize_rcu*() with interrupts disabled

rcu: Permit start_poll_synchronize_rcu*() with interrupts disabled

The header comment for both start_poll_synchronize_rcu() and
start_poll_synchronize_rcu_full() state that interrupts must be enabled
when calling these two functions, and there is a lockdep assertion in
start_poll_synchronize_rcu_common() enforcing this restriction.  However,
there is no need for this restrictions, as can be seen in call_rcu(),
which does wakeups when interrupts are disabled.

This commit therefore removes the lockdep assertion and the comments.

Reported-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>