dm: spi: Add tests

These tests use SPI flash (and the sandbox emulation) to operate.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>

test/dm/test-dm.sh

@@ -4,4 +4,6 @@ NUM_CPUS=$(cat /proc/cpuinfo |grep -c processor)
 dtc -I dts -O dtb test/dm/test.dts -o test/dm/test.dtb
 make O=sandbox sandbox_config
 make O=sandbox -s -j${NUM_CPUS}
+dd if=/dev/zero of=spi.bin bs=1M count=2
 ./sandbox/u-boot -d test/dm/test.dtb -c "dm test"
+rm spi.bin