scripts: get_abi.pl: Better handle multiple What parameters

Using a comma here is problematic, as some What: expressions
may already contain a comma. So, use \xac character instead.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/e83e7ffaf3429f8dfca00d1d01653ecfa36f6119.1631957565.git.mchehab+huawei@kernel.org


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