configs: Add cache region to x86 demo cells

configs: Add cache region to x86 demo cells

Assuming we have more than 4 units of L3 cache on systems that support
L3 partitioning, assign the first 2 units (e.g. 2 MB on a Xeon D 1540)
to apic-demo, the 3rd to tiny-demo. Also the non-root Linux config gets
the first 2 units (it cannot run in parallel to the other demos). All
this is for testing the management logic and will later be used to
benchmark the partitioning.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>