scripts: get_abi.pl: assume ReST format by default

All ABI files are now compatible with ReST format. So, change
the script default to assume that the ABI source files
are compatible with ReST.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/4b0af257010570e0e917d82498e42992bec5e173.1604042072.git.mchehab+huawei@kernel.org


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