MAINTAINERS: change list for KVM/s390

KVM/s390 does not have a list of its own, and linux-s390 is in the
loop anyway thanks to the generic arch/s390 match.  So use the generic
KVM list for s390 patches.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

MAINTAINERS

@@ -8869,7 +8869,7 @@ M:	Christian Borntraeger <borntraeger@de.ibm.com>
 M:	Janosch Frank <frankja@linux.ibm.com>
 R:	David Hildenbrand <david@redhat.com>
 R:	Cornelia Huck <cohuck@redhat.com>
-L:	linux-s390@vger.kernel.org
+L:	kvm@vger.kernel.org
 W:	http://www.ibm.com/developerworks/linux/linux390/
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux.git
 S:	Supported