meta-aspeed: add CONFIG_USE_BOOTCOMMAND snippet

Add a config snippet that sets CONFIG_BOOTCOMMAND to the correct address
on 128MiB flashes.

This requires a refresh of the u-boot sdk patch we've been carrying such
that CONFIG_BOOTCOMMAND is set conditionally if not set previously.

Change-Id: I44adc4236991b718316ab52f0023d20ca5fb5f91
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/recipes-bsp/u-boot/u-boot-aspeed-sdk/flash-131072/bootcmd.cfg b/recipes-bsp/u-boot/u-boot-aspeed-sdk/flash-131072/bootcmd.cfg
new file mode 100644
index 0000000..6862aae
--- /dev/null
+++ b/recipes-bsp/u-boot/u-boot-aspeed-sdk/flash-131072/bootcmd.cfg
@@ -0,0 +1,2 @@
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="bootm 20100000"