meta-ampere: Initial AmpereOne(TM) Mt. Mitchell's non-DC-SCM BMC support

Add new Mt.Mitchell platform with basic features so that it can be
compiled and works.

Tested:
1. Compile for Mt.Mitchell successful.
2. Flash and check for the firmware can boot on the Mt.Mitchell
non-DC-SCM system without issue

Signed-off-by: Chanh Nguyen <chanh@os.amperecomputing.com>
Change-Id: I8dc9db9029b27c0c6325c31d368cdbb614a3c8b6
diff --git a/meta-ampere/meta-mitchell/conf/templates/default/conf-notes.txt b/meta-ampere/meta-mitchell/conf/templates/default/conf-notes.txt
new file mode 100644
index 0000000..9b3c01a
--- /dev/null
+++ b/meta-ampere/meta-mitchell/conf/templates/default/conf-notes.txt
@@ -0,0 +1,2 @@
+Common targets are:
+     obmc-phosphor-image