staging: mt7621-pci: MIPS/ralink: add MT7621 pcie driver

NeilBrown: forward port and hack to work on GNUBEE1
Signed-off-by: John Crispin <blogic@openwrt.org>
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/Makefile

@@ -49,3 +49,4 @@ obj-$(CONFIG_GREYBUS)		+= greybus/
 obj-$(CONFIG_BCM2835_VCHIQ)	+= vc04_services/
 obj-$(CONFIG_DRM_VBOXVIDEO)	+= vboxvideo/
 obj-$(CONFIG_PI433)		+= pi433/
+obj-$(CONFIG_SOC_MT7621)	+= mt7621-pci/

drivers/staging/mt7621-pci/Makefile

+obj-$(CONFIG_SOC_MT7621)       += pci-mt7621.o

drivers/staging/mt7621-pci/TODO

+
+- general code review and cleanup
+- can this be converted to not require PCI_DRIVERS_LEGACY ??
+    The irq returned by pcibios_map_irq is a "hwirq" (hardware irq number)
+    and pci_assign_irq() assigns this directly to dev->irq, which
+    expects a "virq" (virtual irq number).  These numbers are different
+    on MIPS.  There is a gross hack to make it work on one
+    specific platform, so it can be tested.
+- Should this be merged with arch/mips/pci/pci-mt7620.c ??
+- ensure device-tree requirements are documented
+
+Cc:  NeilBrown <neil@brown.name>