The MPS2 FPGAIO block includes some simple free-running counters.
Implement these.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20180820141116.9118-2-peter.maydell@linaro.org