MAINTAINERS: add uv.c also to KVM/s390

Most changes in uv.c are related to KVM. Involve also the KVM team
regarding changes to uv.c.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>

Author: borntraeger

MAINTAINERS

@@ -9674,6 +9674,7 @@ F:	Documentation/virt/kvm/s390*
 F:	arch/s390/include/asm/gmap.h
 F:	arch/s390/include/asm/kvm*
 F:	arch/s390/include/uapi/asm/kvm*
+F:	arch/s390/kernel/uv.c
 F:	arch/s390/kvm/
 F:	arch/s390/mm/gmap.c
 F:	tools/testing/selftests/kvm/*/s390x/