Instead of open-coding a check on the ID_DFR0 PerfMon ID register
field, create a standardly-named isar_feature for "does AArch32 have
a v8.1 PMUv3" and use it.
This entails moving the id_dfr0 field into the ARMISARegisters struct.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20200214175116.9164-9-peter.maydell@linaro.org
(cherry-picked from commit a617953855b65a602d36364b9643f7e5bc31288e)
Signed-off-by: Peng Liang <liangpeng10@huawei.com>
