target/arm: Filter cycle counter based on PMCCFILTR_EL0

target/arm: Filter cycle counter based on PMCCFILTR_EL0

Rename arm_ccnt_enabled to pmu_counter_enabled, and add logic to only
return 'true' if the specified counter is enabled and neither prohibited
or filtered.

Signed-off-by: Aaron Lindsay <alindsay@codeaurora.org>
Signed-off-by: Aaron Lindsay <aclindsa@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20181211151945.29137-5-aaron@os.amperecomputing.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>