linux-aspeed-sdk: g6: Enable UART driver

The ast2600 device tree uses the DesignWare 8250 compatible, so we need
this enabled in order to get a console.

Change-Id: I946b3de87cc2fed703889892c474cd3e5be8a47f
Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/recipes-kernel/linux/linux-aspeed-sdk/aspeed-g6/defconfig b/recipes-kernel/linux/linux-aspeed-sdk/aspeed-g6/defconfig
index 93ecece..92f922c 100644
--- a/recipes-kernel/linux/linux-aspeed-sdk/aspeed-g6/defconfig
+++ b/recipes-kernel/linux/linux-aspeed-sdk/aspeed-g6/defconfig
@@ -179,6 +179,7 @@
 CONFIG_SERIAL_8250_EXTENDED=y
 CONFIG_SERIAL_8250_ASPEED_VUART=y
 CONFIG_SERIAL_8250_SHARE_IRQ=y
+CONFIG_SERIAL_8250_DW=y
 CONFIG_SERIAL_OF_PLATFORM=y
 CONFIG_ASPEED_KCS_IPMI_BMC=y
 CONFIG_ASPEED_BT_IPMI_BMC=y