PCI: designware: Add MSI-related pcie_host_ops for v3.65 hardware

DesignWare v3.65 hardware implements MSI controller registers in
application space.  This requires updates to the DesignWare core to
support controllers based on this older hardware.

Add msi_irq_set()/clear() interfaces to allow Set/Clear MSI IRQ enable bit
in the application register.  Also, v3.65 hardware uses the MSI_IRQ
register in application register space to raise MSI IRQ to the RC from EP.
Current code uses the standard mechanism as per PCI spec.  So add
get_msi_data() to get the address of this register so common code can
work on both v3.65 and newer hardware.

[bhelgaas: changelog]
Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Pratyush Anand <pratyush.anand@st.com>
Acked-by: Mohit Kumar <mohit.kumar@st.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
CC: Russell King <linux@arm.linux.org.uk>
CC: Grant Likely <grant.likely@linaro.org>
CC: Rob Herring <robh+dt@kernel.org>
CC: Richard Zhu <r65037@freescale.com>
CC: Kishon Vijay Abraham I <kishon@ti.com>
CC: Marek Vasut <marex@denx.de>
CC: Arnd Bergmann <arnd@arndb.de>
CC: Pawel Moll <pawel.moll@arm.com>
CC: Mark Rutland <mark.rutland@arm.com>
CC: Ian Campbell <ijc+devicetree@hellion.org.uk>
CC: Kumar Gala <galak@codeaurora.org>
CC: Randy Dunlap <rdunlap@infradead.org>
CC: Grant Likely <grant.likely@linaro.org>