spapr_hcall: Fix h_enter to loop correctly

We wanted to loop till index is 8. On 8 we return with H_PTEG_FULL. If we
are successful in loading hpte with any other index, we continue with that
index value.

Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
