docs(maintainers): add missing header files

Few header files are added to the lists tracking code owners of
various modules in TF-A project.

Also remove drivers/nuvoton directory, which does not exist, from the list
of files maintained by the corresponding owners.

Change-Id: Iad7ce5b1430965237004c9e76e972a3469d20c9d
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
1 file changed