MAINTAINERS: Add Rob Herring and remove Andy Murray as PCI reviewers

Andy Murray decided to step down as PCI controller reviewer and Rob Herring
is willing to help review PCI controller patches.

Update the respective MAINTAINERS entries to reflect this change.

Link: https://lore.kernel.org/r/20200422150336.10528-1-lorenzo.pieralisi@arm.comSigned-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rob Herring <robh@kernel.org>
Cc: Andrew Murray <amurray@thegoodpenguin.co.uk>

MAINTAINERS

@@ -13038,7 +13038,7 @@ F:	drivers/pci/controller/pci-xgene-msi.c
 
 PCI NATIVE HOST BRIDGE AND ENDPOINT DRIVERS
 M:	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
-R:	Andrew Murray <amurray@thegoodpenguin.co.uk>
+R:	Rob Herring <robh@kernel.org>
 L:	linux-pci@vger.kernel.org
 S:	Supported
 Q:	http://patchwork.ozlabs.org/project/linux-pci/list/