These functions become a little bit more reusable if they return a list
containing the output rather than just printing it.

(Bitbake rev: a0ad2a947b71abcc0a1244cf139b9e9dfd8ee049)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>