target/arm/helper: Propagate MDCR_EL2.HPMN into PMCR_EL0.N

target/arm/helper: Propagate MDCR_EL2.HPMN into PMCR_EL0.N

MDCR_EL2.HPMN allows an hypervisor to limit the number of PMU counters
available to EL1 and EL0 (to keep the others to itself). QEMU already
implements this split correctly, except for PMCR_EL0.N reads: the number
of counters read by EL1 or EL0 should be the one configured in
MDCR_EL2.HPMN.

Cc: qemu-stable@nongnu.org
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Message-id: 20231215144652.4193815-2-jean-philippe@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>