MAINTAINERS: s390/pci: add Collin Walling as maintainer for zpci

Collin will take over the maintainership from Yi Min. Let us add a
separate s390 pci section.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <1540827745-20795-4-git-send-email-borntraeger@de.ibm.com>
Acked-by: NCollin Walling <walling@linux.ibm.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>

MAINTAINERS

@@ -956,6 +956,12 @@ F: pc-bios/s390-ccw.img
 T: git git://github.com/borntraeger/qemu.git s390-next
 L: qemu-s390x@nongnu.org
 
+S390 PCI
+M: Collin Walling <walling@linux.ibm.com>
+S: Supported
+F: hw/s390x/s390-pci*
+L: qemu-s390x@nongnu.org
+
 UniCore32 Machines
 -------------
 PKUnity-3 SoC initramfs-with-busybox