staging: xillybus: force to be a module

As reported, this driver causes problems when built into the kernel, so
force it to be a module until those issues are fixed.

Also delete the "default n" lines in the Kconfig, as they are not
needed.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Eli Billauer <eli.billauer@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/xillybus/Kconfig

@@ -4,8 +4,7 @@
 
 config XILLYBUS
 	tristate "Xillybus generic FPGA interface"
-	depends on PCI || (OF_ADDRESS && OF_DEVICE && OF_IRQ)
-	default n
+	depends on PCI || (OF_ADDRESS && OF_DEVICE && OF_IRQ) && m
 	help
 	  Xillybus is a generic interface for peripherals designed on
 	  programmable logic (FPGA). The driver probes the hardware for
@@ -18,7 +17,6 @@ if XILLYBUS
 config XILLYBUS_PCIE
 	tristate "Xillybus over PCIe"
 	depends on XILLYBUS && PCI
-	default n
 	help
 	  Set to M if you want Xillybus to use PCI Express for communicating
 	  with the FPGA.
@@ -26,7 +24,6 @@ config XILLYBUS_PCIE
 config XILLYBUS_OF
 	tristate "Xillybus over Device Tree"
 	depends on XILLYBUS && OF_ADDRESS && OF_DEVICE && OF_IRQ
-	default n
 	help
 	  Set to M if you want Xillybus to find its resources from the
 	  Open Firmware Flattened Device Tree. If the target is an embedded