linux-yocto-*: change linux-yocto recipe to target boards rather than
architecture, to allow for zedboard and zc702 builds.

Signed-off-by: Sipke Vriend <sipke.vriend@xilinx.com>
linux-yocto: add kc705-trd as target machine.

Add kc705-trd as compatible machine to linux-yocto recipe.
Add standard kernel type fragments for kc705-trd.

Signed-off-by: Sipke Vriend <sipke.vriend@xilinx.com>