Add u-boot for Palmetto

Ported from http://github.com/facebook/openbmc.
diff --git a/meta-palmetto/conf/machine/palmetto.conf b/meta-palmetto/conf/machine/palmetto.conf
index 82a9b1c..0efdda0 100644
--- a/meta-palmetto/conf/machine/palmetto.conf
+++ b/meta-palmetto/conf/machine/palmetto.conf
@@ -18,9 +18,14 @@
        obmc-phosphor-example-pydbus \
        "
 
-# UBOOT_MACHINE_${MACHINE} = "${MACHINE}_config
 KMACHINE = "aspeed"
 KERNEL_DEVICETREE = "${KMACHINE}-bmc-opp-${MACHINE}.dtb"
 
 require conf/machine/include/ast2400.inc
 require conf/machine/include/obmc-bsp-common.inc
+
+UBOOT_MACHINE_palmetto = "palmetto_config"
+UBOOT_ENTRYPOINT = "0x40008000"
+UBOOT_LOADADDRESS = "0x40008000"
+
+FLASH_SIZE = "32768"