KVM: arm64: nv: Handle ZCR_EL2 traps

Unlike other SVE-related registers, ZCR_EL2 takes a sysreg trap to EL2
when HCR_EL2.NV = 1. KVM still needs to honor the guest hypervisor's
trap configuration, which expects an SVE trap (i.e. ESR_EL2.EC = 0x19)
when CPTR traps are enabled for the vCPU's current context.

Otherwise, if the guest hypervisor has traps disabled, emulate the
access by mapping the requested VL into ZCR_EL1.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240620164653.1130714-4-oliver.upton@linux.dev


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>