rtl8xxxu: Switch 8192cu/8188cu devices to use rtl8xxxu_init_queue_reserved_page()

This was the last user of the old
rtl8xxxu_old_init_queue_reserved_page() which can now be removed.

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