efi_loader: endless loop in add_strings_package()

Avoid an endless loop in add_strings_package().
Suggested-by: NTakahiro Akashi <takahiro.akashi@linaro.org>
Reported-by: Coverity (CID 185833)
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>

lib/efi_loader/efi_hii.c

@@ -227,9 +227,8 @@ out:
 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);