ppc: make cpu_model translation to type consistent

ppc: make cpu_model translation to type consistent

PPC handles -cpu FOO rather incosistently,
i.e. it does case-insensitive matching of FOO to
a CPU type (see: ppc_cpu_compare_class_name) but
handles alias names as case-sensitive, as result:

 # qemu-system-ppc64 -M mac99 -cpu g3
 qemu-system-ppc64: unable to find CPU model ' kN�U'

 # qemu-system-ppc64 -cpu 970MP_V1.1
 qemu-system-ppc64: Unable to find sPAPR CPU Core definition

while

 # qemu-system-ppc64 -M mac99 -cpu G3
 # qemu-system-ppc64 -cpu 970MP_v1.1

start up just fine.

Considering we can't take case-insensitive matching away,
make it case-insensitive for  all alias/type/core_type
lookups.

As side effect it allows to remove duplicate core types
which are the same except of using different cased letters in name.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>