staging: r8188eu: use in-kernel arc4 encryption

Replace custom arc4 implementation with in-kernel one.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20210903190444.15585-3-straube.linux@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>