xen/common: add cache coloring common code

Last Level Cache (LLC) coloring allows to partition the cache in smaller
chunks called cache colors.

Since not all architectures can actually implement it, add a HAS_LLC_COLORING
Kconfig option.
LLC_COLORS_ORDER Kconfig option has a range maximum of 10 (2^10 = 1024)
because that's the number of colors that fit in a 4 KiB page when integers
are 4 bytes long.

LLC colors are a property of the domain, so struct domain has to be extended.

Based on original work from: Luca Miccio <lucmiccio@gmail.com>

Signed-off-by: Carlo Nonato <carlo.nonato@minervasys.tech>
Signed-off-by: Marco Solieri <marco.solieri@minervasys.tech>
Acked-by: Michal Orzel <michal.orzel@amd.com>

SUPPORT.md

@@ -401,6 +401,13 @@ by maintaining multiple physical to machine (p2m) memory mappings.
     Status, x86 HVM: Tech Preview
     Status, ARM: Tech Preview
 
+### Cache coloring
+
+Allows to reserve Last Level Cache (LLC) partitions for Dom0, DomUs and Xen
+itself.
+
+    Status, Arm64: Experimental
+
 ## Resource Management
 
 ### CPU Pools