drivers/rtc: correct an error test

rtc is clearly does not satisfy IS_ERR at the point where it is tested, so
I have changed the test to consider the just initialized rtc->rtc_dev.

The semantic match that finds the problem is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@match exists@
expression x, E;
identifier fld;
position p1,p2;
@@

(
x = E;
|
x = E
|
x@p1->fld
... when != x = E
IS_ERR(x@p2)
... when any
)

@other_match exists@
expression match.x, E1, E2;
position match.p1,match.p2;
@@

x = E1
... when != x = E2
    when != x@p1
x@p2

@ script:python depends on !other_match@
p1 << match.p1;
p2 << match.p2;
@@

print "* file %s dereference %s test %s" % (p1[0].file,p1[0].line,p2[0].line)
// </smpl>

Signed-off-by: Julia Lawall <[email protected]>
Acked-by: Alessandro Zummo <[email protected]>
Cc: David Brownell <[email protected]>
Cc: Bryan Wu <[email protected]>
Cc: Mike Frysinger <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

drivers/rtc/rtc-bfin.c

@@ -390,7 +390,7 @@ static int __devinit bfin_rtc_probe(struct platform_device *pdev)
 
 	/* Register our RTC with the RTC framework */
 	rtc->rtc_dev = rtc_device_register(pdev->name, dev, &bfin_rtc_ops, THIS_MODULE);
-	if (unlikely(IS_ERR(rtc))) {
+	if (unlikely(IS_ERR(rtc->rtc_dev))) {
 		ret = PTR_ERR(rtc->rtc_dev);
 		goto err_irq;
 	}