machine-xilinx-default.inc: Remove linux-yocto version pinning
machine-xilinx-default.inc: Remove linux-yocto version pinning

Use the newest available on targets that default to using linux-yocto.

Signed-off-by: Nathan Rossi <2e8aa918660411855c6d44d5bb2da677aa033255@nathanrossi.com>
Acked-by: Alistair Francis <52ecf00b70a50079ae8d5fa09b9af6904950b63c@xilinx.com>

Xilinx/meta-xilinx,Xilinx/meta-xilinx,Xilinx/meta-xilinx,nathanrossi/meta-xilinx,nathanrossi/meta-xilinx,Xilinx/meta-xilinx,Xilinx/meta-xilinx,nathanrossi/meta-xilinx,Xilinx/meta-xilinx,nathanrossi/meta-xilinx