KVM: PPC: Move processor compatibility check to module init

Move KVM PPC's compatibility checks to their respective module_init()
hooks, there's no need to wait until KVM's common compat check, nor is
there a need to perform the check on every CPU (provided by common KVM's
hook), as the compatibility checks operate on global data.

  arch/powerpc/include/asm/cputable.h: extern struct cpu_spec *cur_cpu_spec;
  arch/powerpc/kvm/book3s.c: return 0
  arch/powerpc/kvm/e500.c: strcmp(cur_cpu_spec->cpu_name, "e500v2")
  arch/powerpc/kvm/e500mc.c: strcmp(cur_cpu_spec->cpu_name, "e500mc")
                             strcmp(cur_cpu_spec->cpu_name, "e5500")
                             strcmp(cur_cpu_spec->cpu_name, "e6500")

Cc: Fabiano Rosas <farosas@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Message-Id: <20221130230934.1014142-27-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>