efi_loader: Check that the bootflow is not removed by app

The bootflow should not be affected by the app running and returning.
Add a check that it is still valid after the app completes execution.

Signed-off-by: Simon Glass <sjg@chromium.org>

test/boot/bootflow.c

@@ -1330,6 +1330,9 @@ static int bootflow_efi(struct unit_test_state *uts)
 
 	ut_assert_console_end();
 
+	/* make sure the bootflow is still present */
+	ut_assertnonnull(std->cur_bootflow);
+
 	/* check memory allocations are as expected */
 	if (!hdr)
 		return 0;