SLUB: Fix format specifier in Documentation/vm/slabinfo.c

There's a little problem in Documentation/vm/slabinfo.c
The code is using "%d" in a printf() call to print an 'unsigned long'.
This patch corrects it to use "%lu" instead.

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Christoph Lameter <clameter@sgi.com>