MAINTAINERS: add reviewers for some s390 areas

MAINTAINERS: add reviewers for some s390 areas

To improve review coverage, assign additional people as reviewers for
multiple s390 sections.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Acked-by: Jason J. Herne <jjherne@linux.ibm.com>
Acked-by: Collin Walling <walling@linux.ibm.com>
Acked-by: Jared Rossi <jrossi@linux.ibm.com>
Acked-by: Halil Pasic <pasic@linux.ibm.com>
Acked-by: Farhan Ali <alifm@linux.ibm.com>
Acked-by: Zhuoying Cai <zycai@linux.ibm.com>
Acked-by: Eric Farman <farman@linux.ibm.com>
Message-ID: <20250623160030.98281-1-mjrosato@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>