MAINTAINERS: Add entries for PPC64 RPA PCI hotplug drivers

Add myself as maintainer of the IBM RPA hotplug modules in the
drivers/pci/hotplug directory.  These modules provide kernel interfaces for
support of Dynamic Logical Partitioning (DLPAR) of Logical and Physical IO
slots, and hotplug of physical PCI slots of a PHB on RPA-compliant ppc64
platforms (pseries).

Signed-off-by: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>