fix(measured-boot): add missing image identifier string

The case for SPD=spmd was not handled.

Signed-off-by: Tamas Ban <tamas.ban@arm.com>
Change-Id: I6c6f268aeb0db15d41662bea81f4a9255e1fabe9
diff --git a/include/drivers/measured_boot/metadata.h b/include/drivers/measured_boot/metadata.h
index 66d826c..5e17a83 100644
--- a/include/drivers/measured_boot/metadata.h
+++ b/include/drivers/measured_boot/metadata.h
@@ -43,6 +43,8 @@
 #define MBOOT_BL32_IMAGE_STRING		"SECURE_RT_EL1_TLKD"
 #elif defined(SPD_trusty)
 #define MBOOT_BL32_IMAGE_STRING		"SECURE_RT_EL1_TRUSTY"
+#elif defined(SPD_spmd)
+#define MBOOT_BL32_IMAGE_STRING		"SECURE_RT_EL1_SPMD"
 #else
 #define MBOOT_BL32_IMAGE_STRING		"SECURE_RT_EL1_UNKNOWN"
 #endif /* SPD_opteed */