rtl8xxxu: Fix 8188RU support

The 8188RU does not like PAPE to be enabled, while all the other gen1
parts seem to require it.

This makes the RTL8188RU able to associate for me.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>