rcn: add the beagle-xm to the dd image list

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
script: with am335x_boneblack make sure to use the am335x_evm script

Reported-by: Cody Lacey <clacey@ti.com>
Signed-off-by: Robert Nelson <robertcnelson@gmail.com>