hwmon: Add missing inclusions of <linux/err.h>

These drivers use IS_ERR so they should include <linux/err.h>.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Luca Tettamanti <kronos.it@gmail.com>
Cc: Henrik Rydberg <rydberg@euromail.se>
diff --git a/drivers/hwmon/ibmpex.c b/drivers/hwmon/ibmpex.c
index 41dbf81..b622a93 100644
--- a/drivers/hwmon/ibmpex.c
+++ b/drivers/hwmon/ibmpex.c
@@ -26,6 +26,7 @@
 #include <linux/jiffies.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
+#include <linux/err.h>
 
 #define REFRESH_INTERVAL	(2 * HZ)
 #define DRVNAME			"ibmpex"