sato/images: Add ptest image

We need an image containing the ptest packages for testing purposes. This adds such an image based on sato-sdk. We did try appending this in the autobuilder but it creates too much confusion about what is going on, and increases build time due to lack of parallelisation.

new file mode 100644
index 0000000..93e5a4e
@@ -0,0 +1,6 @@
+require core-image-sato-sdk.bb
+
+DESCRIPTION += "Also includes ptest packages."
+
+IMAGE_FEATURES += "ptest-pkgs"
+