[U-Boot] libfdt SWIG build error with Python 3.x

In some Linux distributions (e.g., Arch Linux) the Python binary points to Python 3.x instead of Python 2.x. This is an issue when building the libfdt SWIG extension, as the generated extension file will be called something like _libfdt.cpython-36m-x86_64-linux-gnu.so instead of just _libfdt.so. By simply changing python to python2 in tools/Makefile this issue goes away. Should I submit a patch to fix this ?