HiSax: fix error checking for hisax_register()]

This patch (as875) adds error-checking to the callers of hisax_register().
It also changes an error pathway in that routine, making it return an error
code rather than 0.

This fixes Bugzilla #7960.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Karsten Keil <kkeil@suse.de>
Cc: Martin Bachem <info@colognechip.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/isdn/hisax/config.c b/drivers/isdn/hisax/config.c
index da4196f..8d53a7f 100644
--- a/drivers/isdn/hisax/config.c
+++ b/drivers/isdn/hisax/config.c
@@ -1551,7 +1551,7 @@
 	if (retval == 0) { // yuck
 		cards[i].typ = 0;
 		nrcards--;
-		return retval;
+		return -EINVAL;
 	}
 	cs = cards[i].cs;
 	hisax_d_if->cs = cs;