scripts/spdxcheck: Add [sub]directory statistics

scripts/spdxcheck: Add [sub]directory statistics

Add functionality to display [sub]directory statistics. This is enabled by
adding '-d' to the command line. The optional -D parameter allows to limit
the directory depth. If supplied the subdirectories are accumulated

# scripts/spdxcheck.py -d kernel/
Incomplete directories: SPDX in Files
    ./kernel                         :   111 of   114   97%
    ./kernel/bpf                     :    43 of    45   95%
    ./kernel/bpf/preload             :     4 of     5   80%
    ./kernel/bpf/preload/iterators   :     4 of     5   80%
    ./kernel/cgroup                  :    10 of    13   76%
    ./kernel/configs                 :     0 of     9    0%
    ./kernel/debug                   :     3 of     4   75%
    ./kernel/debug/kdb               :     1 of    11    9%
    ./kernel/locking                 :    29 of    32   90%
    ./kernel/sched                   :    38 of    39   97%

The result can be accumulated by restricting the depth via the new command
line option '-d $DEPTH':

# scripts/spdxcheck.py -d -D1
Incomplete directories: SPDX in Files
    ./                               :     6 of    13   46%
    ./Documentation                  :  4096 of  8451   48%
    ./arch                           : 13476 of 16402   82%
    ./block                          :   100 of   101   99%
    ./certs                          :    11 of    14   78%
    ./crypto                         :   145 of   176   82%
    ./drivers                        : 24682 of 30745   80%
    ./fs                             :  1876 of  2110   88%
    ./include                        :  5175 of  5757   89%
    ./ipc                            :    12 of    13   92%
    ./kernel                         :   493 of   527   93%
    ./lib                            :   393 of   524   75%
    ./mm                             :   151 of   159   94%
    ./net                            :  1713 of  1900   90%
    ./samples                        :   211 of   273   77%
    ./scripts                        :   341 of   435   78%
    ./security                       :   241 of   250   96%
    ./sound                          :  2438 of  2503   97%
    ./tools                          :  3810 of  5462   69%
    ./usr                            :     9 of    10   90%

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>