hw/arm/aspeed: Set default CPU count using aspeed_soc_num_cpus()

hw/arm/aspeed: Set default CPU count using aspeed_soc_num_cpus()

Since commit b7f1a0cb76 ("arm/aspeed: Compute the number
of CPUs from the SoC definition") Aspeed machines use the
aspeed_soc_num_cpus() helper to set the number of CPUs.

Use it for the ast1030-evb (commit 356b230ed1 "aspeed/soc:
Add AST1030 support") and supermicrox11-bmc (commit 40a38df55e
"hw/arm/aspeed: Add board model for Supermicro X11 BMC") machines.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>