A few corrections to include/linux/Kbuild

auxvec.h, i2c-dev.h and vt.h *should* be unifdef'ed i2o-dev.h does not need
unifdef'ing

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>