[S390] add __ucmpdi2() helper function

Provide __ucmpdi2() helper function on 31 bit so we don't run
again and again in compile errors like this one:

kernel/built-in.o: In function `T.689':
perf_counter.c:(.text+0x56c86): undefined reference to `__ucmpdi2'
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/lib/Makefile

@@ -3,6 +3,6 @@
 #
 
 lib-y += delay.o string.o uaccess_std.o uaccess_pt.o
-obj-$(CONFIG_32BIT) += div64.o qrnnd.o
+obj-$(CONFIG_32BIT) += div64.o qrnnd.o ucmpdi2.o
 lib-$(CONFIG_64BIT) += uaccess_mvcos.o
 lib-$(CONFIG_SMP) += spinlock.o

arch/s390/lib/ucmpdi2.c

+#include <linux/module.h>
+
+union ull_union {
+	unsigned long long ull;
+	struct {
+		unsigned int high;
+		unsigned int low;
+	} ui;
+};
+
+int __ucmpdi2(unsigned long long a, unsigned long long b)
+{
+	union ull_union au = {.ull = a};
+	union ull_union bu = {.ull = b};
+
+	if (au.ui.high < bu.ui.high)
+		return 0;
+	else if (au.ui.high > bu.ui.high)
+		return 2;
+	if (au.ui.low < bu.ui.low)
+		return 0;
+	else if (au.ui.low > bu.ui.low)
+		return 2;
+	return 1;
+}
+EXPORT_SYMBOL(__ucmpdi2);