Modification to include dtb files as well in machine images tarball.

* Selection criteria was using machine-name alongwith other patterns
to pick the file. Since some dtb file names didn't contain exact
machine-name they were left out. Removed ${MACHINE}* so that such
necessary files are also included in the tar.

Signed-off-by: Fahad Arslan <fahad_arslan@mentor.com>