s390: make use of user_mode() macro where possible

We use the user_mode() helper already at several places but also
have the open coded variant at other places.
Convert the code to always use the helper function.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/oprofile/backtrace.c b/arch/s390/oprofile/backtrace.c
index c82f62f..8a6811b 100644
--- a/arch/s390/oprofile/backtrace.c
+++ b/arch/s390/oprofile/backtrace.c
@@ -58,7 +58,7 @@
 	unsigned long head;
 	struct stack_frame* head_sf;
 
-	if (user_mode (regs))
+	if (user_mode(regs))
 		return;
 
 	head = regs->gprs[15];