Remove config variable DEBUG_RWLOCK, since it is not used.

Signed-off-by: Jiri Olsa <olsajiri@gmail.com>
Acked-by: Grant Grundler <grundler@parisc-linux.org>
Acked-by: Kyle McMartin <kyle@mcmartin.ca>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>