PCI: dwc/dra7xx: Use the common MSI irq_chip

PCI: dwc/dra7xx: Use the common MSI irq_chip

The dra7xx MSI irq_chip implementation is identical to the default DWC one.
The only difference is the interrupt handler as the MSI interrupt is muxed
with other interrupts, but that doesn't affect the irq_chip part of it.

Link: https://lore.kernel.org/r/20201105211159.1814485-7-robh@kernel.org
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-omap@vger.kernel.org