[PATCH] x86-64: use BUILD_BUG_ON in FPU code

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>