weboslayers.py: Comment newly added MACHINE-s list

:Release Notes:
List of valid MACHINE-s was added in https://gpro.palm.com/46208/
This change adds comments as suggested by Herb Kuta in that review.

:Detailed Notes:

:Testing Performed:
Only build tested

:QA Notes:
No change to image.

:Issues Addressed:
[ES-468] Support checking mcf MACHINE arguments for validity

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: I6a6557a99dce4706e966b7cc5d5b7b47334a61ba
Reviewed-on: https://g2g.palm.com/6154
Reviewed-by: DCO Verification
Build: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Martin Jansa <Martin.Jansa@lge.com>
Tested-by: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Build Verification
Reviewed-by: Susan Montooth <susan.montooth@lge.com>

weboslayers.py

@@ -46,11 +46,13 @@
 #
 # working-dir = Alternative directory for the layer.
 #
-# The name of the distribution is also defined in this file.
+# The name of the distribution is also defined in this file
+# along with a list of the valid MACHINE-s
 #
 
 Distribution = "webos"
 
+# Supported MACHINE-s
 Machines = ['qemux86', 'qemuarm']
 
 # github.com/openembedded repositories are read-only mirrors of the authoritative