Revert "staging:r8188eu: Use lib80211 to encrypt (TKIP) tx frames"

This reverts commit 0d4876f4 as it
breaks the build once 4.18-rc7 was merged into the staging-next tree.

Cc: Ivan Safonov <insafonov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>