test: let use gdbserver for all sandbox targets

Enable usage of gdbserver for all sandbox targets (sandbox,
sandbox_flattree etc.).

Signed-off-by: Igor Opaniuk <igor.opaniuk@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed