ARM: dts: msm: assign each PCIe root complex a domain

Currently, the framework assigns each root complex a domain number
on a first come first served basis. This is not ideal as the wrong
domain number may be assigned if the root complexes are not probed
in order. This change will assign each root complex a domain number
based on their node.

Change-Id: I9e10137b410af8df552a3d27d9de0e7b5c40a678
Signed-off-by: Tony Truong <truong@codeaurora.org>