ibm: palmetto: Use v2019.04-aspeed-openbmc u-boot tree

The OpenBMC u-boot tree now has support for the AST2400 based Palmetto
and can use a single configuration for NCSI and non-NCSI boards.

Change-Id: I7190b09bdffbfe045bb7c140bd5626932e86bdb6
Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/meta-ibm/meta-palmetto/conf/machine/palmetto.conf b/meta-ibm/meta-palmetto/conf/machine/palmetto.conf
index d34b7b0..5a92152 100644
--- a/meta-ibm/meta-palmetto/conf/machine/palmetto.conf
+++ b/meta-ibm/meta-palmetto/conf/machine/palmetto.conf
@@ -6,11 +6,8 @@
 require conf/machine/include/openpower.inc
 require conf/machine/include/p8.inc
 
-PREFERRED_PROVIDER_virtual/bootloader = "u-boot-aspeed"
-PREFERRED_PROVIDER_u-boot = "u-boot-aspeed"
-PREFERRED_PROVIDER_u-boot-fw-utils = "u-boot-fw-utils-aspeed"
-
-UBOOT_MACHINE:palmetto = "ast_g4_ncsi_config"
+UBOOT_MACHINE = "evb-ast2400_defconfig"
+UBOOT_DEVICETREE = "ast2400-palmetto"
 UBOOT_ENTRYPOINT = "0x40008000"
 UBOOT_LOADADDRESS = "0x40008000"