wl12xx: enable sparse endianess check by default

Following the good example of the Intel (and more recently Atheros)
drivers, enable endianess check by default when running sparse.
Signed-off-by: Luciano Coelho <coelho@ti.com>

drivers/net/wireless/wl12xx/Makefile

@@ -11,3 +11,5 @@ obj-$(CONFIG_WL12XX_SDIO)		+= wl12xx_sdio.o
 
 # small builtin driver bit
 obj-$(CONFIG_WL12XX_PLATFORM_DATA)	+= wl12xx_platform_data.o
+
+ccflags-y += -D__CHECK_ENDIAN__