powerpc/fsl: add MSI support for the Freescale hypervisor

Add support for vmpic-msi nodes to the fsl_msi driver.  The MSI is
virtualized by the hypervisor, so the vmpic-msi does not contain a 'reg'
property.  Instead, the driver uses hcalls.

Add support for the "msi-address-64" property to the fsl_pci driver.
The Freescale hypervisor typically puts the virtualized MSIIR register
in the page after the end of DDR, so we extend the DDR ATMU to cover it.
Any other location for MSIIR is not supported, for now.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>