KVM: arm64: pmu: Use arm_pmuv3.h register accessors

Commit df29ddf4 ("arm64: perf: Abstract system register accesses
away") split off PMU register accessor functions to a standalone header.
Let's use it for KVM PMU code and get rid one copy of the ugly switch
macro.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Tested-by: James Clark <james.clark@linaro.org>
Link: https://lore.kernel.org/r/20240731-arm-pmu-3-9-icntr-v3-3-280a8d7ff465@kernel.org


Signed-off-by: Will Deacon <will@kernel.org>