MAINTAINERS: Replace backup for s390 vfio-pci

Farhan has been doing a masterful job coming on in the
s390 PCI space, and my own attention has been lacking.
Let's make MAINTAINERS reflect reality.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
Acked-by: Alex Williamson <alex@shazbot.org>
Acked-by: Farhan Ali <alifm@linux.ibm.com>
Acked-by: Matthew Rosato <mjrosato@linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

Author: efarman

MAINTAINERS

@@ -23072,7 +23072,8 @@ F:	include/uapi/linux/vfio_ccw.h
 
 S390 VFIO-PCI DRIVER
 M:	Matthew Rosato <mjrosato@linux.ibm.com>
-M:	Eric Farman <farman@linux.ibm.com>
+M:	Farhan Ali <alifm@linux.ibm.com>
+R:	Eric Farman <farman@linux.ibm.com>
 L:	linux-s390@vger.kernel.org
 L:	kvm@vger.kernel.org
 S:	Supported