KVM: s390: MAINTAINERS: promote Claudio Imbrenda

Claudio has volunteered to be more involved in the maintainership of
s390 KVM.

Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20220210085310.26388-1-borntraeger@linux.ibm.com

MAINTAINERS

@@ -10547,8 +10547,8 @@ F:	arch/riscv/kvm/
 KERNEL VIRTUAL MACHINE for s390 (KVM/s390)
 M:	Christian Borntraeger <borntraeger@linux.ibm.com>
 M:	Janosch Frank <frankja@linux.ibm.com>
+M:	Claudio Imbrenda <imbrenda@linux.ibm.com>
 R:	David Hildenbrand <david@redhat.com>
-R:	Claudio Imbrenda <imbrenda@linux.ibm.com>
 L:	kvm@vger.kernel.org
 S:	Supported
 W:	http://www.ibm.com/developerworks/linux/linux390/