When PCI_COMMAND_MEMORY/PCI_COMMAND_IO are cleared, the bridge should not
allocate windows or even look at the window limit/base registers.

Otherwise we may set up bogus windows while the PCI core code performs
discovery.  The core will leave PCI_COMMAND_IO cleared if it doesn't need
an IO window.

Have mvebu_pcie_handle_*_change respect the bits, and call the change
function whenever the bits changes.
Tested-by: NThomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: NJason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: NJason Cooper <jason@lakedaemon.net>