scripts: get_abi.pl: change script to allow parsing in ReST mode

Right now, several ABI files won't parse as ReST, as they
contain severe violations to the spec, with makes the script
to crash.

So, the code has a sanity logic with escapes bad code and
cleans tags that can cause Sphinx to crash.

Add support for disabling this mode.

Right now, as enabling rst-mode causes crash, it is disabled
by default.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/34b691e3002e8987c24d851fe37640f95e506a92.1604042072.git.mchehab+huawei@kernel.org


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