checkpatch: emit a warning on embedded filenames

Embedding the complete filename path inside the file isn't particularly
useful as often the path is moved around and becomes incorrect.

Emit a warning when the source contains the filename.

[akpm@linux-foundation.org: remove stray " di"]

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/1fd5f9188a14acdca703ca00301ee323de672a8d.camel@perches.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>