Revert "cfg80211: reg: remove support for built-in regdb"

This reverts commit c8c240e2.

Restore support for internal regulatory database. It is
needed since Android does not have CRDA.
Fix checker errors related to defconfig files.

Change-Id: Ie60e0f4dd450c6efbbc8643e01c946bc11b557ee
Signed-off-by: Lior David <liord@codeaurora.org>