mel: define a sane default for MELDIR

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
mel: break up DEPLOY_DIR_IMAGE by PACKAGE_ARCH

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Layer updates per current oe-core master

Signed-off-by: Christopher Larson <chris_larson@mentor.com>