MAINTAINERS: add missing files to the adis lib

The triggered buffer support was missing in the MAINTAINERS file. Add
them.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220122130905.99-1-nuno.sa@analog.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>