include/asm-generic: Remove spin_is_locked() comment

The WARN_ON_SMP() comment header suggests using spin_is_locked() to
check for locks being held.  But these days we prefer lockdep_assert_held(),
so this commit removes that suggestion.
Signed-off-by: NPaul E. McKenney <paulmck@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: <linux-arch@vger.kernel.org>

include/asm-generic/bug.h

@@ -211,9 +211,6 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 /*
  * WARN_ON_SMP() is for cases that the warning is either
  * meaningless for !SMP or may even cause failures.
- * This is usually used for cases that we have
- * WARN_ON(!spin_is_locked(&lock)) checks, as spin_is_locked()
- * returns 0 for uniprocessor settings.
  * It can also be used with values that are only defined
  * on SMP:
  *