The PYNQ boards identify themselves as a generic Xilinx 7000
chip in the device tree, and, somewhat annoyingly, do not
include board-level information in the board name or list of
compats. Specific board information can, however, be queried
directly from a separate device-tree file.
Use the device tree compatible value to detect which Jetson board the
code is running on, rather than the DT model value. The compatible value
should be more stable. This algorithm exactly matches how Jetson.GPIO
detects boards, so allows easier porting of new board support between
the two code-bases.