aarch64: add core okl4 hypervisor config

Adds the OKL4_GUEST config to the arm64 architecture, which
serves as a root selector to enable additional drivers for
running on the OKL4 hypervisor.

include/asm-generic/okl4_virq.h:
  A generic helper for OKL4 hypervisor aware drivers.

Change-Id: Ie89c5341cad762812485115bbe45c3bb4a1d7a15
Signed-off-by: Carl van Schaik <carl@cog.systems>
Git-commit: 936194027fc9abaacec9b253c0f3e468a3d51577
Git-repo: https://github.com/CogSystems/linux-msm/commits/msm-4.9-hyp


Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>
Signed-off-by: Prakruthi Deepak Heragu <pheragu@codeaurora.org>