beaglebone-yocto: rename beaglebone machine to beaglebone-yocto

beaglebone-yocto: rename beaglebone machine to beaglebone-yocto

The beaglebone BSP provided in this layer is a reference implementation
usingonly mainline components available in core Yocto Project layers,
whereas Texas Instruments maintain a full-featured BSP in the meta-ti
layer.

Rename the reference machine to prevent namespace collisions with the
version maintained by the SoC vendor.

[YOCTO #12326]

(From meta-yocto rev: e32882938eca7f50548deab84dab78b4aef31b95)

Signed-off-by: Joshua Lock <joshua.g.lock@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>