Fix asserts appearing in release builds

Also fix warnings generated in release builds when assert code
is absent.

Change-Id: I45b9173d3888f9e93e98eb5b4fdc06727ba5cbf4
diff --git a/common/bl_common.c b/common/bl_common.c
index 0a0c5cd..d401f8c 100644
--- a/common/bl_common.c
+++ b/common/bl_common.c
@@ -272,8 +272,9 @@
 			 unsigned int load_type,
 			 unsigned long fixed_addr)
 {
-	unsigned long temp_image_base, image_base;
-	long offset;
+	unsigned long temp_image_base = 0;
+	unsigned long image_base = 0;
+	long offset = 0;
 	int image_flen;
 
 	/* Find the size of the image */