Remove BR2_DEPRECATED

Remove BR2_DEPRECATED

The BR2_DEPRECATED logic is a lot less useful than the legacy handling,
because the symbols just disappears without warning to the user. For
example, we had a few defconfigs that were using deprecated symbols
(which were not actually used because BR2_DEPRECATED wasn't set) so
these didn't build the expected code anymore.

Also, the idea behind BR2_DEPRECATED is that you can easily revive it
again if there is interest. However, it is relatively easy to revert
the removal of a package as well.

The deprecation is also more effort because it has to be removed twice:
once when deprecating, and once when really removing.

It doesn't make sense to add a legacy entry for BR2_DEPRECATED. Users
who actually used it will get legacy warnings instead.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>