[RCAR] Enable Linux-based hypervisor execution in AGL

[RCAR] Enable Linux-based hypervisor execution in AGL

The upstream version of AGL boots Linux in EL1. This mode is not
privileged enough to put in place the correct configuration of
an hypervisor (e.g., KVM).

This patch leverages the ATF rcar platform configuration variables to
boot the Linux kernel in EL2, instead of EL1, allowing Linux-based
hypervisors such as KVM to configure all the necessary stubs to
properly run virtual machines.

This patch has been successfully tested with ATF, KVM and AGL rootfs
on the Renesas R-Car M3.

Changelog:
- Added arm-trusted-firmware patch, which makes this work easy
  to be tested by the community
- This patch version does not contain Linux kernel modifications.
  In fact, these resulted not necessary with the proposed ATF patch
  and a recent kernel (higher than 4.6)

Bug-AGL: SPEC-497
Bug-AGL: SPEC-1571
Signed-off-by: Michele Paolino <m.paolino@virtualopensystems.com>
Signed-off-by: Ronan Le Martret <ronan.lemartret@iot.bzh>
Change-Id: I8d20e36a09be1dba35b10193643ea00e4f388e95
Signed-off-by: Ronan Le Martret <ronan.lemartret@iot.bzh>