recipes-devtools: Add serial-test recipe
recipes-devtools: Add serial-test recipe

Recipe comes from layer meta-bec:
git://github.com/cbrake/linux-serial-test.git
commit 6bcdd65adab4883638140a22c1fbf4a199a1d4fc

Signed-off-by: Janine Hagemann <8d93c2f2f444ad47da091bc753c1a540a7335a92@phytec.de>
Signed-off-by: Stefan Müller-Klieser <a3e08e35e4a42be768e7d0e76ae1ba321c2a66dd@phytec.de>

PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec