drivers/char: Fix implicit use of err.h in ramoops.c

drivers/char/ramoops.c: In function 'ramoops_init':
drivers/char/ramoops.c:221: error: implicit declaration of function 'IS_ERR'
drivers/char/ramoops.c:222: error: implicit declaration of function 'PTR_ERR'
make[3]: *** [drivers/char/ramoops.o] Error 1

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/char/ramoops.c b/drivers/char/ramoops.c
index 810aff9..7c7f42a1f8 100644
--- a/drivers/char/ramoops.c
+++ b/drivers/char/ramoops.c
@@ -26,6 +26,7 @@
 #include <linux/module.h>
 #include <linux/kmsg_dump.h>
 #include <linux/time.h>
+#include <linux/err.h>
 #include <linux/io.h>
 #include <linux/ioport.h>
 #include <linux/platform_device.h>