Fixes [YOCTO #5554]
Applied edits to the section in the dev-manual on running tests
on hardware.
Edited the TEST_TARGET and TEST_IMAGE variables.
(From yocto-docs rev: a26ba11c739aabab4009a944d9b622e2814c7fca)
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>