atmel_lcdfb: change irq_base definition to allow error reporting

Changed because old the definition of unsigned long cannot be negative.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Reported-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/video/atmel_lcdc.h

@@ -38,7 +38,7 @@ struct atmel_lcdfb_info {
 	spinlock_t		lock;
 	struct fb_info		*info;
 	void __iomem		*mmio;
-	unsigned long		irq_base;
+	int			irq_base;
 	struct work_struct	task;
 
 	unsigned int		guard_time;