UPSTREAM: PCI: rockchip: cleanup for rockchip pcie driver

UPSTREAM: PCI: rockchip: cleanup for rockchip pcie driver

Bjorn did some cleanup for rockchip pcie driver after
mereging the drivers. So let's backport it entirely
to keep consisten with the upstream kernel.

[bhelgaas: fold in Brian's rockchip_pcie_client_irq_handler() OR fix, other
fixes and cleanups from Guenter Roeck <linux@roeck-us.net> and me,
uninitialized variable fix from Arnd Bergmann <arnd@arndb.de>]

Change-Id: If680b9c2264cd89561427180b146c34eb8549511
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>