kconfig: fix time ordering of writes to .kconfig.d and include/linux/autoconf.h

Since .kconfig.d is used as a make dependency of include/linux/autoconf.h, it
should be written earlier than the header file, to avoid a subsequent rebuild
to consider the header outdated.

Signed-Off-By: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>