efi_loader: endless loop in add_strings_package()

Avoid an endless loop in add_strings_package().

Suggested-by: Takahiro Akashi <takahiro.akashi@linaro.org>
Reported-by: Coverity (CID 185833)
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/efi_loader/efi_hii.c b/lib/efi_loader/efi_hii.c
index 3a966fa..61b71de 100644
--- a/lib/efi_loader/efi_hii.c
+++ b/lib/efi_loader/efi_hii.c
@@ -227,9 +227,8 @@
 error:
 	if (stbl) {
 		free(stbl->language);
-		if (idx > 0)
-			while (--idx >= 0)
-				free(stbl->strings[idx].string);
+		while (idx > 0)
+			free(stbl->strings[--idx].string);
 		free(stbl->strings);
 	}
 	free(stbl);