BACKPORT: arm/arm64: Probe for the presence of KVM hypervisor

Although the SMCCC specification provides some limited functionality for
describing the presence of hypervisor and firmware services, this is
generally applicable only to functions designated as "Arm Architecture
Service Functions" and no portable discovery mechanism is provided for
standard hypervisor services, despite having a designated range of
function identifiers reserved by the specification.

In an attempt to avoid the need for additional firmware changes every
time a new function is added, introduce a UID to identify the service
provider as being compatible with KVM. Once this has been established,
additional services can be discovered via a feature bitmap.

BUG=b:230005239
BUG=b:230582047
TEST=tast run arc.Boot.vm

Backport-notes:
Fix merge conflicts which comes from upstream patch applying order.

Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
[maz: move code to its own file, plug it into PSCI]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@google.com>
Link: https://lore.kernel.org/r/20201209060932.212364-2-jianyong.wu@arm.com
(cherry picked from commit 6e085e0a)
Change-Id: I2d5b8eedf71858b01a9fa5bdf5d62b55ab379fb6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3848978


Commit-Queue: Suleiman Souhlal <suleiman@chromium.org>
Reviewed-by: Suleiman Souhlal <suleiman@chromium.org>