accel/hvf: Use accel-specific per-vcpu @dirty field

accel/hvf: Use accel-specific per-vcpu @dirty field

HVF has a specific use of the CPUState::vcpu_dirty field
(CPUState::vcpu_dirty is not used by common code).
To make this field accel-specific, add and use a new
@dirty variable in the AccelCPUState structure.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20240424174506.326-4-philmd@linaro.org>