hw/dma/pl080: Don't use hw_error() for unimplemented features

In the pl080 device, we don't implement "peripheral flow control", which is where the DMA engine can be programmed to transfer data until a source or destination peripheral tells it to stop. We currently call hw_error() if the guest tries to use this missing feature, which prints a register dump and aborts QEMU. Change the hw_error() call to the LOG_UNIMP log-and-continue, which is how we prefer to report guest attempts to use unimplemented features these days. Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3409 Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Message-id: 20260529143624.158935-3-peter.maydell@linaro.org