KVM: MIPS: Move .vcpu_setup() call to kvm_arch_vcpu_create()

Fold setup() into create() now that the two are called back-to-back by
common KVM code.  This paves the way for removing kvm_arch_vcpu_setup().
Note, there is no unwind function associated with kvm_arch_vcpu_setup(),
i.e. no teardown path that also needs to be moved.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>