layerscape: add ls-rcw-bin package

NXP LSDK1712 release used two rcw git trees. The
original rcw git tree was still source code but
dropping ls1012a/ls1088a/ls2088a boards in LSDK1712.
Instead another new rcw git tree was used to just
provided rcw binaries for these boards dropped. So
this patch is to update ls-rcw to LSDK1712 release
and add a new ls-rcw-bin package.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>