kconfig: reset generated values only if Kconfig and .config agree.

Normally generated values (Kconfig entries without a prompt) are cleared as
they are regenerated anyway and so they appear as new should they become
visible and defaults work as expected (once a value is set defaults aren't
used anymore).

The detection whether a value is generated or not is only based on its
visibility status, which can quickly change for a lot of symbols by just
removing a single line from .config or adding a dependency to Kconfig as you
noticed.

The patch now suppresses this logic when .config and Kconfig aren't in sync
and .config needs to be updated, so that you can remove now a random value
from .config and oldconfig won't reask for many other values.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>