msm: adsprpc: RPC driver between apps and adsp

The driver implements an IPC (Inter-Processor) communication
mechanism that allows for clients to make remote method
invocations across processor boundary.

Change-Id: I95710df16e9258ad37b1f3d1e32f36003760b970
Acked-by: Sathish Ambley <sambley@qualcomm.com>
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>