signal: Use lockdep_assert_held instead of assert_spin_locked

signal: Use lockdep_assert_held instead of assert_spin_locked

The distinction is that assert_spin_locked() checks if the lock is
held *by*anyone* whereas lockdep_assert_held() asserts the current
context holds the lock.  Also, the check goes away if you build
without lockdep.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/Ympr/+PX4XgT/UKU@hirez.programming.kicks-ass.net
Tested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lkml.kernel.org/r/20220505182645.497868-6-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>