target-ppc: Add PMC5/6, SDAR and MMCRA to 970 family

target-ppc: Add PMC5/6, SDAR and MMCRA to 970 family

MMCR0, MMCR1, MMCRA, PMC1..6, SIAR, SDAR are defined for 970 and PowerISA
CPUs. Since we are building common infrastructure for SPRs intialization
to share it between 970 and POWER5+/7/..., let's add missing SPRs to
the 970 family. Later rework of CPU class initialization will use those
for all PowerISA CPUs.

This adds new SPRs and enables writing to Uxxxx SPRs from supermode.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Alexander Graf <agraf@suse.de>