The default, 970fx, doesn't support MSR_LE. So even though we set LE in
ppc_cpu_reset, it gets cleared again in hreg_store_msr. Error out if a
user-selected cpu model doesn't support LE.
Signed-off-by: Richard Henderson <rth@twiddle.net>
[agraf: switch to POWER7 as default for BE and LE]
Signed-off-by: Alexander Graf <agraf@suse.de>