Install diffstat test suite and run it as ptest.
(From OE-Core rev: 63cf8ab1ffdb04278aeb28b6ffce22ff7b272e29)
Signed-off-by: Chong Lu <Chong.Lu@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>