Revert "Revert "mediapad_defconfig: enable SElinux""

This reverts commit 0e26ea8131bcbed9decd329e57d244407006b286.
Revert "mediapad_defconfig: enable SElinux" + HACK

This reverts commit 5fe474bed7a5eb2cea1a0cbfb7d367dc3385dd6c. (reverted from commit 0e26ea8131bcbed9decd329e57d244407006b286)