ARM: mxs: select SPARSE_IRQ

With icoll and gpio interrupt controllers adopt irqdomain support and
all interrupt nubmers are retrieved from device tree, it's safe to
select SPARSE_IRQ for mxs now.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 7207086..58bffb3 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -491,6 +491,7 @@
 	select HAVE_CLK_PREPARE
 	select MULTI_IRQ_HANDLER
 	select PINCTRL
+	select SPARSE_IRQ
 	select USE_OF
 	help
 	  Support for Freescale MXS-based family of processors