rtc: bunch of drivers: fix 'no irq' case handing

This patch fixes a bunch of irq checking misuses.  Most drivers were
getting irq via platform_get_irq(), which returns -ENXIO or r->start.

rtc-cmos.c is special.  It is using PNP and platform bindings.  Hopefully
nobody is using PNP IRQ 0 for RTC.  So the changes should be safe.

rtc-sh.c is using platform_get_irq, but was storing a result into an
unsigned type, then was checking for < 0.  This is fixed now.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/rtc/rtc-at32ap700x.c b/drivers/rtc/rtc-at32ap700x.c
index 90b9a65..e1ec33e 100644
--- a/drivers/rtc/rtc-at32ap700x.c
+++ b/drivers/rtc/rtc-at32ap700x.c
@@ -205,7 +205,7 @@
 {
 	struct resource	*regs;
 	struct rtc_at32ap700x *rtc;
-	int irq = -1;
+	int irq;
 	int ret;
 
 	rtc = kzalloc(sizeof(struct rtc_at32ap700x), GFP_KERNEL);
@@ -222,7 +222,7 @@
 	}
 
 	irq = platform_get_irq(pdev, 0);
-	if (irq < 0) {
+	if (irq <= 0) {
 		dev_dbg(&pdev->dev, "could not get irq\n");
 		ret = -ENXIO;
 		goto out;