3c59x.c's vortex_timer() function knows that vp->lock can only be used by an
irq context that it disabled - and can hence take the vp->lock without
disabling hardirqs.  Teach lockdep about this.

Has no effect on non-lockdep kernels.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>