Enable USB gadget ECM support in kernel config

The USB gadget ECM enables the BMC to enumrate as an ethernet device to
the host.

Signed-off-by: Lei YU <yulei.sh@bytedance.com>
Change-Id: I87bcf0bf61f37d77f7b70e2aae07525b55583748
diff --git a/recipes-kernel/linux/linux-aspeed_%.bbappend b/recipes-kernel/linux/linux-aspeed_%.bbappend
new file mode 100644
index 0000000..a8255c5
--- /dev/null
+++ b/recipes-kernel/linux/linux-aspeed_%.bbappend
@@ -0,0 +1,3 @@
+FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+
+SRC_URI += " file://usbctl.cfg"