external/mambo: Add POWER10 small-core mode
external/mambo: Add POWER10 small-core mode

If the SMT configuration is not 8, set small-core mode in SIM_CTRL1
and PVR registers.

Also allow only 1, 2, 4, or 8 threads, and only allow 1 and 2 threads
if there is only one processor configured. This helps avoid strange
crashes due to thread/core enumeration problems with unexpected threads
per core.

Signed-off-by: Nicholas Piggin <24829078df5003d9dd1dd871ca2aeb0b1cf95ef4@gmail.com>
Signed-off-by: Vasant Hegde <a6d753843573f7bfed5075c1e875b0be8007a0ab@linux.vnet.ibm.com>

shenki/skiboot,qemu/skiboot,legoater/skiboot,open-power/skiboot,shenki/skiboot,shenki/skiboot,legoater/skiboot,open-power/skiboot,open-power/skiboot,open-power/skiboot,qemu/skiboot,legoater/skiboot,shenki/skiboot,open-power/skiboot,qemu/skiboot,qemu/skiboot,qemu/skiboot,legoater/skiboot,shenki/skiboot,legoater/skiboot