Get rid of warnings when compiled with -Wformat-security

Change-Id: I2a79fc4809cd91cfd2948777eafd256ca2b3041f
diff --git a/exif.c b/exif.c
index f7a6365..3747bf6 100644
--- a/exif.c
+++ b/exif.c
@@ -564,12 +564,12 @@
             // Show tag name
             for (a=0;;a++){
                 if (a >= (int)TAG_TABLE_SIZE){
-                    printf(IndentString);
+                    printf("%s", IndentString);
                     printf("    Unknown Tag %04x Value = ", Tag);
                     break;
                 }
                 if (TagTable[a].Tag == Tag){
-                    printf(IndentString);
+                    printf("%s", IndentString);
                     printf("    %s = ",TagTable[a].Desc);
                     break;
                 }