scripts: get_abi.pl: Allow optionally record from where a line came from

scripts: get_abi.pl: Allow optionally record from where a line came from

The get_abi.pl reads a lot of files and can join them on a
single output file. Store where each "What:" output came from,
in order to be able to optionally display it.

This is useful for the Sphinx extension, with can now be
able to blame what ABI file has issues, and on what line
the What: description with problems begin.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/befc387011c5e3c6febd285b7f27610e41c90260.1604042072.git.mchehab+huawei@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>