[PATCH] slab: remove SLAB_DMA

SLAB_DMA is an alias of GFP_DMA. This is the last one so we
remove the leftover comment too.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>