feat(qemu): add A55 cpu support for virt

Add support to "cortex-a55" cpu for "qemu" ('virt') platform.

Change-Id: I2693892be735eda91494b767322935ddb63c9f48
diff --git a/plat/qemu/common/common.mk b/plat/qemu/common/common.mk
index b8b57d2..b341d25 100644
--- a/plat/qemu/common/common.mk
+++ b/plat/qemu/common/common.mk
@@ -17,6 +17,7 @@
 else
 QEMU_CPU_LIBS		:=	lib/cpus/aarch64/aem_generic.S		\
 				lib/cpus/aarch64/cortex_a53.S		\
+				lib/cpus/aarch64/cortex_a55.S		\
 				lib/cpus/aarch64/cortex_a57.S		\
 				lib/cpus/aarch64/cortex_a72.S		\
 				lib/cpus/aarch64/cortex_a76.S		\