feat(cros_widevine): add ChromeOS widevine SMC handler

The ChromeOS will use the SMC to pass some secrets from firmware to
optee.

Change-Id: Iaf3357d40a7ed22415926acd9d7979df24dd81f1
Signed-off-by: Yi Chou <yich@google.com>
diff --git a/bl31/bl31.mk b/bl31/bl31.mk
index 40e3df8..9959a3e 100644
--- a/bl31/bl31.mk
+++ b/bl31/bl31.mk
@@ -161,6 +161,10 @@
 				${MBEDTLS_SOURCES}
 endif
 
+ifeq ($(CROS_WIDEVINE_SMC),1)
+BL31_SOURCES		+=	services/oem/chromeos/widevine_smc_handlers.c
+endif
+
 BL31_DEFAULT_LINKER_SCRIPT_SOURCE := bl31/bl31.ld.S
 
 ifneq ($(findstring gcc,$(notdir $(LD))),)