kbuild: move files that don't check __KERNEL__

Move files that don't check __KERNEL__ from unifdef-y to header-y.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>