tracing/blktrace: fix up checkpatch reported problems in ftrace plugin patch

Also make sure sparse (make C=2 block/blktrace.o) is happy too.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index 1dba349..59b4b2e 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -142,6 +142,9 @@
 
 #ifdef __KERNEL__
 #if defined(CONFIG_BLK_DEV_IO_TRACE)
+
+#include <linux/sysfs.h>
+
 struct blk_trace {
 	int trace_state;
 	struct rchan *rchan;
@@ -192,6 +195,8 @@
 extern int blk_trace_startstop(struct request_queue *q, int start);
 extern int blk_trace_remove(struct request_queue *q);
 
+extern struct attribute_group blk_trace_attr_group;
+
 #else /* !CONFIG_BLK_DEV_IO_TRACE */
 #define blk_trace_ioctl(bdev, cmd, arg)		(-ENOTTY)
 #define blk_trace_shutdown(q)			do { } while (0)