ARM: dts: Cygnus: Fixed iProc PCIe controller properties

Rename the msi controller unit name to 'msi' to avoid collisions with
the 'msi-controller' boolean property. We also need to re-arrange the
'ranges' property to show the two cells as being separate instead of
combined since the DT checker is not able to differentiate otherwise.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>