rtl8xxxu: Set correct bit to reset MCU IO wrapper

All chips, except for 8812 require BIT(0) for resetting the MCU IO
wrapper. 8723b requires a more complicated reset sequence, so it will
need a custom reset function.

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