dt-bindings: vcpu_stall_detector: Add qemu,vcpu-stall-detector compatible

dt-bindings: vcpu_stall_detector: Add qemu,vcpu-stall-detector compatible

The VCPU stall detection mechanism allows to configure the expiration
duration and the internal counter clock frequency measured in Hz.
Add these properties in the schema.

While this is a memory mapped virtual device, it is expected to be loaded
when the DT contains the compatible: "qemu,vcpu-stall-detector" node.
In a protected VM we trust the generated DT nodes and we don't rely on
the host to present the hardware peripherals.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Ene <sebastianene@google.com>
Link: https://lore.kernel.org/r/20220711081720.2870509-2-sebastianene@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>