target/arm: Rename pmu_8_n feature test functions

Our feature test functions that check the PMU version are named
isar_feature_{aa32,aa64,any}_pmu_8_{1,4}.  This doesn't match the
current Arm ARM official feature names, which are FEAT_PMUv3p1 and
FEAT_PMUv3p4.  Rename these functions to _pmuv3p1 and _pmuv3p4.

This commit was created with:
  sed -i -e 's/pmu_8_/pmuv3p/g' target/arm/*.[ch]

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220822132358.3524971-8-peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>