dm: test: Add test case for dev->dma_offset

Add test to validate dev->dma_offset is properly set on devices.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index 0c7674e..fc1df31 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -108,6 +108,7 @@
 CONFIG_BOOTP_SEND_HOSTNAME=y
 CONFIG_NETCONSOLE=y
 CONFIG_IP_DEFRAG=y
+CONFIG_DM_DMA=y
 CONFIG_REGMAP=y
 CONFIG_SYSCON=y
 CONFIG_DEVRES=y