PCI: mvebu: Add suspend/resume support

Add suspend/resume support for the mvebu PCIe host driver.  Without this
commit, the system will panic at resume time when PCIe devices are
connected.

Note that we have to use the ->suspend_noirq() and ->resume_noirq() hooks,
because at resume time, the PCI fixups are done at ->resume_noirq() time,
so the PCIe controller has to be ready at this point.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Jason Cooper <jason@lakedaemon.net>