feat(spm): add VM_ID macro to spm tests

Add helper macro to define an FF-A ID for a NWd VM. Replaced all found
instances in spm related tests.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I9605898a9cc8ebc90c783e590907ab1ec684c4f7
diff --git a/include/runtime_services/spm_common.h b/include/runtime_services/spm_common.h
index f4b5a75..91a3b8c 100644
--- a/include/runtime_services/spm_common.h
+++ b/include/runtime_services/spm_common.h
@@ -41,6 +41,7 @@
  */
 #define SP_ID_MASK	U(1 << 15)
 #define SP_ID(x)	((x) | SP_ID_MASK)
+#define VM_ID(x)	(x & ~SP_ID_MASK)
 #define IS_SP_ID(x)	((x & SP_ID_MASK) != 0U)
 
 struct ffa_features_test {