KVM: arm64: Initialise hyp_nr_cpus for nVHE hyp

KVM: arm64: Initialise hyp_nr_cpus for nVHE hyp

Knowing the number of CPUs is necessary for determining the boundaries
of per-cpu variables, which will be used for upcoming hypervisor
tracing. hyp_nr_cpus which stores this value, is only initialised for
the pKVM hypervisor. Make it accessible for the nVHE hypervisor as well.

With the kernel now responsible for initialising hyp_nr_cpus, the
nr_cpus parameter is no longer needed in __pkvm_init.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Link: https://patch.msgid.link/20260309162516.2623589-22-vdonnefort@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>