scripts: get_abi.pl: improve debug logic

Add a level for debug, in order to allow it to be extended to
debug other parts of the script.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/0203416c6c418abb4fc20577a5f48d0d2a41bae7.1632411447.git.mchehab+huawei@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>