irqchip/xilinx: Expose Kconfig option

Previously the XILINX_INTC config option was hidden and only
auto-selected on the MicroBlaze platform. However, this IP can also be
used on other platforms. Allow this option to be user-enabled.

Signed-off-by: Robert Hancock <robert.hancock@calian.com>

drivers/irqchip/Kconfig

@@ -288,8 +288,12 @@ config XTENSA_MX
 	select GENERIC_IRQ_EFFECTIVE_AFF_MASK
 
 config XILINX_INTC
-	bool
+	bool "Xilinx Interrupt Controller IP"
 	select IRQ_DOMAIN
+	help
+	  Support for the Xilinx Interrupt Controller IP core.
+	  This is used as a primary controller with MicroBlaze and can also
+	  be used as a secondary chained controller on other platforms.
 
 config IRQ_CROSSBAR
 	bool