u-boot-aspeed: Disable unnecessary features

Allow platforms to opt into the u-boot patch disabling unnecessary
hardware features for ASPEED SoCs.

As this change touches bits that were not initialised by previous u-boot
revisions and the configuration applied prevents poweron of OpenPOWER
hosts without corresponding host firmware changes, this change is
nohwci.

Change-Id: I0248de6882fff0f6bd00a859bb9c2883969831fc
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/conf/distro/include/phosphor-isolation.inc b/conf/distro/include/phosphor-isolation.inc
new file mode 100644
index 0000000..007f676
--- /dev/null
+++ b/conf/distro/include/phosphor-isolation.inc
@@ -0,0 +1,2 @@
+DISTRO_FEATURES += "isolate-bmc"
+DISTROOVERRIDES .= ":df-isolate-bmc"