scripts: get_abi.pl: use bold font for ABI definitions

As we're using tables, let's distinguish the ones used by ABI
by using a bold font.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/9ed645c2519169817379c1df5b8cf03828e92520.1604042072.git.mchehab+huawei@kernel.org


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