drivers tty: add okl4_vtty driver

Adds a driver which provides console and TTY using the OKL4
hypervisor pipe IPC facility.

Change-Id: Iccbb9eda626fd90d3cc6494c490e13d51edfe42a
Signed-off-by: Carl van Schaik <carl@cog.systems>
Git-commit: 53d0af02d807f4224d29912788e265eec23dd12d
Git-repo: https://github.com/CogSystems/linux-msm/commits/msm-4.9-hyp


[mnalajal@codeaurora: Resolve trivial merge conflicts in Kconfig]
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>
[pheragu@codeaurora: Replace proc_fops with proc_show]
Signed-off-by: Prakruthi Deepak Heragu <pheragu@codeaurora.org>