manifest: Require 'compatible' property in 'hypervisor' node

Other hypervisors also use a 'hypervisor' node in the FDT to pass
config information to the VMs. Add requirement to specify which
hypervisors the node is compatible with. The 'compatible' property
is a list of NULL-separated strings in the format
"<manufacturer>,<model>". Following the naming convention of other
projects, we will use "hafnium,hafnium" as a match-all-versions value,
and later add "hafnium,hafnium_<version>" values to match specific
releases of Hafnium.

Bug: 117551352
Change-Id: Ie6dadcdace37318d4d122e80fefe989715ee9cc9
diff --git a/test/linux/manifest.dts b/test/linux/manifest.dts
index 5437968..f863c6e 100644
--- a/test/linux/manifest.dts
+++ b/test/linux/manifest.dts
@@ -18,6 +18,7 @@
 
 / {
 	hypervisor {
+		compatible = "hafnium,hafnium";
 		vm1 {
 			debug_name = "primary";
 		};