u-boot-aspeed: Fix fw_env.config for ast2600

The configuration was not set at all, leaving us with the default
configuration file from u-boot.

This sets it to the u-boot environment partition, /dev/mtd2.

Change-Id: Ic7439c057151763273b35435d0414adeac3ef76a
Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/recipes-bsp/u-boot/files/fw_env_ast2600_nor.config b/recipes-bsp/u-boot/files/fw_env_ast2600_nor.config
new file mode 100644
index 0000000..ccd037e
--- /dev/null
+++ b/recipes-bsp/u-boot/files/fw_env_ast2600_nor.config
@@ -0,0 +1,2 @@
+# MTD device name	Device offset	Env. size	Flash sector size	Number of sectors
+/dev/mtd/u-boot-env	0x0000		0x10000		0x1000