feat(realm): assign MECID when creating realms

This change allows TFTF to assign a MECID to every realm that is
created by passing an extra parameter to the Realm creation helpers.

Signed-off-by: Juan Pablo Conde <juanpablo.conde@arm.com>
Change-Id: I89bf08011eb005d949a195b406b073955f23f5ad
diff --git a/include/lib/aarch64/arch_helpers.h b/include/lib/aarch64/arch_helpers.h
index f562018..6847ce3 100644
--- a/include/lib/aarch64/arch_helpers.h
+++ b/include/lib/aarch64/arch_helpers.h
@@ -733,6 +733,9 @@
 DEFINE_RENAME_SYSREG_RW_FUNCS(tpidr_el2, TPIDR_EL2)
 DEFINE_RENAME_SYSREG_RW_FUNCS(vtcr_el2, VTCR_EL2)
 
+/* Memory Encryption Contexts (MEC) */
+DEFINE_RENAME_SYSREG_READ_FUNC(mecidr_el2, MECIDR_EL2)
+
 static inline u_register_t read_sp(void)
 {
 	u_register_t v;