Fixed ARM-software/tf-issues#603

Updated optee_utils.c to fix ARM-software/tf-issues#603 related to the
tee-validate-header bug.

Minor updates to the header valid checking logic. It would never make
sense to have less than 1 image to load so this is now checked.

Changed OPTEE_MAX_IMAGE_NUM to OPTEE_MAX_NUM_IMAGES to clarify its
definition. OPTEE_MAX_IMAGE_NUM sounds like an ID assigned to the last
image to load. OPTEE_MAX_NUM_IMAGES sounds like the maximum number of
images to load.
Signed-off-by: Nathan Menhorn <nathan.menhorn@xilinx.com>

lib/optee/optee_utils.c

@@ -25,7 +25,8 @@ typedef struct optee_image {
 
 #define OPTEE_PAGER_IMAGE_ID		0
 #define OPTEE_PAGED_IMAGE_ID		1
-#define OPTEE_MAX_IMAGE_NUM		2
+
+#define OPTEE_MAX_NUM_IMAGES		2u
 
 #define TEE_MAGIC_NUM_OPTEE		0x4554504f
 /*
@@ -53,14 +54,20 @@ typedef struct optee_header {
  ******************************************************************************/
 static inline int tee_validate_header(optee_header_t *header)
 {
+	int valid = 0;
+
 	if ((header->magic == TEE_MAGIC_NUM_OPTEE) &&
-		(header->version == 2) &&
-		(header->nb_images <= OPTEE_MAX_IMAGE_NUM)) {
-		return 1;
+		(header->version == 2u) &&
+		(header->nb_images > 0u) &&
+		(header->nb_images <= OPTEE_MAX_NUM_IMAGES)) {
+		valid = 1;
 	}
 
+	else {
 		WARN("Not a known TEE, use default loading options.\n");
-	return 0;
+	}
+
+	return valid;
 }
 
 /*******************************************************************************