CHROMIUM: BACKPORT: FROMLIST: dt-bindings: cpufreq: add bindings for virtual kvm cpufreq

Add devicetree bindings for a virtual kvm cpufreq driver.

Co-developed-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: David Dai <davidai@google.com>
(am from https://patchwork.kernel.org/patch/13195011/)
(also found at https://lore.kernel.org/r/20230330224348.1006691-6-davidai@google.com

)

Modify:
  Add "^virtual,.*" entry to Documentation/devicetree/bindings/vendor-prefixes.yaml

BUG=b:249685960
TEST=Build
UPSTREAM-TASK=b:256983979

Change-Id: Iff8727878345c8f034cc07a11a37f697d0f0634e
Signed-off-by: Masami Hiramatsu <mhiramat@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/4444927


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