meta-evb-ast2600: Add an new convenience layer for OpenBMC AST2600 EVB

This commit has been verified with AST2600A1 EVB with the image created
by the following command:

TEMPLATECONF=meta-evb/meta-evb-aspeed/meta-evb-ast2600/conf . openbmc-env
bitbake obmc-phosphor-image

(From meta-evb rev: 9ec0661731103f703660aa65b5806a126a4f69fb)

Signed-off-by: Troy Lee <troy_lee@aspeedtech.com>
Change-Id: Ie928880ed77ea77cecb33a900092f6ffc5454fb8
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/meta-evb/meta-evb-aspeed/meta-evb-ast2600/conf/conf-notes.txt b/meta-evb/meta-evb-aspeed/meta-evb-ast2600/conf/conf-notes.txt
new file mode 100644
index 0000000..9b3c01a
--- /dev/null
+++ b/meta-evb/meta-evb-aspeed/meta-evb-ast2600/conf/conf-notes.txt
@@ -0,0 +1,2 @@
+Common targets are:
+     obmc-phosphor-image