KVM: PPC: e500: Call kvmppc_mmu_map for initial mapping

When emulating tlbwe, we want to automatically map the entry that just got
written in our shadow TLB map, because chances are quite high that it's
going to be used very soon.

Today this happens explicitly, duplicating all the logic that is in
kvmppc_mmu_map() already. Just call that one instead.

Signed-off-by: Alexander Graf <agraf@suse.de>