[PATCH] include/linux/kernel.h:BUILD_BUG_ON(): fix a comment

Fix comment describing BUILD_BUG_ON: BUG_ON is not an assertion
(unfortunately).

Signed-off-by: Nikita Danilov <nikita@clusterfs.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>