Most of the platforms have 3 or more viewports.  For such platforms, We do
not need to share viewports between IO and CFG.  Assign viewport 2 to IO
transactions in such cases.
Tested-by: NDong Bo <dongbo4@huawei.com>
Signed-off-by: NPratyush Anand <pratyush.anand@gmail.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: NRob Herring <robh@kernel.org>