msm: ipc: Add device tree support

IPC Router is configured using local tables that do not allow
customization on a per-target basis.

Add device tree support to configure IPC Router.

CRs-Fixed: 543252
Change-Id: Id546a9780b2c491205a3ac9757d18f2c3a4d4632
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>