Prevent stuff like this:

mm/vmalloc.c: In function 'unmap_kernel_range':
mm/vmalloc.c:75: warning: unused variable 'start'

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>