drivers misc: add okl4-link-shbuf driver

A simple driver for using a shared-memory bridge between two
VMs.

Change-Id: I3dac6dd88d1f658c95e799262a9720a44af00291
Signed-off-by: Carl van Schaik <carl@cog.systems>
Git-commit: 18b0192bb16d90974af0401f1a46f20f0f5b9502
Git-repo: https://github.com/CogSystems/linux-msm.git


Signed-off-by: Minming Qi <mqi@codeaurora.org>