maintainers: improve coverage of arch-specific files

maintainers: improve coverage of arch-specific files

The sub-directories of config/ are maintained by
different architecture maintainers.

Some wildcards are used to describe the lib, drivers and app files
which are specific to some architectures.

The EAL Arm files have split responsibilities depending on 32/64 suffix,
and the common files are shared between Armv7 and Armv8 sections.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: David Christensen <drc@linux.vnet.ibm.com>
Acked-by: David Marchand <david.marchand@redhat.com>