PCI: microchip: Enable building driver as a module

Enable building driver as a module. The expected use case is the
driver is built as a module, is installed when needed, and cannot be
removed once installed since it is not possible to clean-up
the irq_chip data structures on removal, as described in:

https://lore.kernel.org/linux-pci/[email protected]/

The driver has .suppress_bind_attrs set to true for the same
reasons (ie prevent unbinding, that would leave the kernel
with stale IRQ configuration that cannot be cleaned up).

Link: https://lore.kernel.org/linux-pci/[email protected]/
Link: https://lore.kernel.org/r/[email protected]
Suggested-by: Uwe Kleine-König <[email protected]>
Signed-off-by: Daire McNamara <[email protected]>
Signed-off-by: Lorenzo Pieralisi <[email protected]>
Acked-by: Conor Dooley <[email protected]>

Author: Daire McNamara

drivers/pci/controller/Kconfig

@@ -217,7 +217,7 @@ config PCIE_MT7621
 	  This selects a driver for the MediaTek MT7621 PCIe Controller.
 
 config PCIE_MICROCHIP_HOST
-	bool "Microchip AXI PCIe controller"
+	tristate "Microchip AXI PCIe controller"
 	depends on PCI_MSI && OF
 	select PCI_HOST_COMMON
 	help

drivers/pci/controller/pcie-microchip-host.c

@@ -1135,5 +1135,6 @@ static struct platform_driver mc_pcie_driver = {
 };
 
 builtin_platform_driver(mc_pcie_driver);
+MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Microchip PCIe host controller driver");
 MODULE_AUTHOR("Daire McNamara <[email protected]>");