scripts/make_fit: Print DT name before libfdt errors

scripts/make_fit: Print DT name before libfdt errors

This makes it easier to pinpoint where the error happened. For example:

  FIT     arch/powerpc/boot/image.fit
Error processing arch/powerpc/boot/dts/microwatt.dtb:
Traceback (most recent call last):
  File "/home/jn/dev/linux/linux-git/build-mpc83xx/../scripts/make_fit.py", line 335, in <module>
    sys.exit(run_make_fit())
             ^^^^^^^^^^^^^^
  File "/home/jn/dev/linux/linux-git/build-mpc83xx/../scripts/make_fit.py", line 309, in run_make_fit
    out_data, count, size = build_fit(args)
                            ^^^^^^^^^^^^^^^
  File "/home/jn/dev/linux/linux-git/build-mpc83xx/../scripts/make_fit.py", line 286, in build_fit
    raise e
  File "/home/jn/dev/linux/linux-git/build-mpc83xx/../scripts/make_fit.py", line 283, in build_fit
    (model, compat, files) = process_dtb(fname, args)
                             ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jn/dev/linux/linux-git/build-mpc83xx/../scripts/make_fit.py", line 231, in process_dtb
    model = fdt.getprop(0, 'model').as_str()
            ^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/libfdt.py", line 448, in getprop
    pdata = check_err_null(fdt_getprop(self._fdt, nodeoffset, prop_name),
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/libfdt.py", line 153, in check_err_null
    raise FdtException(val)
libfdt.FdtException: pylibfdt error -1: FDT_ERR_NOTFOUND

Signed-off-by: J. Neuschäfer <j.ne@posteo.net>
Link: https://lore.kernel.org/r/20250209-makefit-v1-1-bfe6151e8f0a@posteo.net
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>