Add Portwell Neptune machine

Initial introduction of Portwell Neptune family equipped with
Aspeed 2500 BMC SoC.

Tested: Build portwell neptune board and load on the target hardware.
Ensure that BMC boots to console.

Change-Id: I7a97162dfe3031904e27f2de2691e693079c9216
Signed-off-by: Amithash Prasad <amithash@fb.com>
diff --git a/meta-portwell/meta-neptune/recipes-kernel/linux/linux-obmc_%.bbappend b/meta-portwell/meta-neptune/recipes-kernel/linux/linux-obmc_%.bbappend
new file mode 100644
index 0000000..761e2ab
--- /dev/null
+++ b/meta-portwell/meta-neptune/recipes-kernel/linux/linux-obmc_%.bbappend
@@ -0,0 +1,2 @@
+FILESEXTRAPATHS_prepend := "${THISDIR}/linux-obmc:"
+SRC_URI += "file://neptune.cfg"