MIPS: KVM: remove the stale memory alias support function unalias_gfn

The memory alias support has been removed since a1f4d395 (KVM: Remove
memory alias support). So remove unalias_gfn from the MIPS port.
Reviewed-by: NJames Hogan <james.hogan@imgtec.com>
Signed-off-by: NDeng-Cheng Zhu <dengcheng.zhu@imgtec.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/mips/kvm/kvm_mips.c

@@ -61,11 +61,6 @@ static int kvm_mips_reset_vcpu(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
-gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
-{
-	return gfn;
-}
-
 /* XXXKYMA: We are simulatoring a processor that has the WII bit set in Config7, so we
  * are "runnable" if interrupts are pending
  */