drivers/rtc/rtc-jz4740.c: fix IRQ error check

Author: Lars-Peter Clausen <lars@metafoo.de>

The irq field of the jz4740_irc struct is unsigned.  Yet we assign the
result of platform_get_irq() to it.  platform_get_irq() may return a
negative error code and the code checks for this condition by checking if
'irq' is less than zero.  But since 'irq' is unsigned this test will
always be false.  Fix it by making 'irq' signed.

The issue was found using the following coccinelle semantic patch:

//
@@
type T;
unsigned T i;
@@
(
*i < 0
|
*i >= 0
)
//

Signed-off-by: Lars-Peter Clausen 
Cc: Alessandro Zummo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 

---
 drivers/rtc/rtc-jz4740.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
 
diff --git a/drivers/rtc/rtc-jz4740.c b/drivers/rtc/rtc-jz4740.c
index 05ab227..1224182 100644
--- a/drivers/rtc/rtc-jz4740.c
+++ b/drivers/rtc/rtc-jz4740.c
@@ -42,7 +42,7 @@ struct jz4740_rtc {
 
 	struct rtc_device *rtc;
 
-	unsigned int irq;
+	int irq;
 
 	spinlock_t lock;
 };