PCI: iproc: Allow BCMA bus driver to be built as module

Change CONFIG_PCIE_IPROC_BCMA to tristate to make it possible to build this
driver as a module.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Ray Jui <rjui@broadcom.com>

drivers/pci/host/Kconfig

@@ -135,7 +135,7 @@ config PCIE_IPROC_PLATFORM
 	  through the generic platform bus interface
 
 config PCIE_IPROC_BCMA
-	bool "Broadcom iProc PCIe BCMA bus driver"
+	tristate "Broadcom iProc PCIe BCMA bus driver"
 	depends on ARCH_BCM_IPROC || (ARM && COMPILE_TEST)
 	select PCIE_IPROC
 	select BCMA