The header file <linux/pfn.h> doesn't exist in userspace and probably
shouldn't -- but it's used unconditionally in <asm-i386/setup.h>.  Protect it
with #ifdef __KERNEL__ and move setup.h from $(header-y) to $(unifdef-y) in
Kbuild accordingly.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>