KVM: arm64: Narrow PMU sysreg reset values to architectural requirements

A number of the PMU sysregs expose reset values that are not
compliant with the architecture (set bits in the RES0 ranges,
for example).

This in turn has the effect that we need to pointlessly mask
some register fields when using them.

Let's start by making sure we don't have illegal values in the
shadow registers at reset time. This affects all the registers
that dedicate one bit per counter, the counters themselves,
PMEVTYPERn_EL0 and PMSELR_EL0.

Reported-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20210719123902.1493805-2-maz@kernel.org