proc_sysctl.c: use BUG_ON instead of BUG

The use of if (!head) BUG(); can be replaced with the single line
BUG_ON(!head).

Signed-off-by: Prasad Joshi <prasadjoshi.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/proc_sysctl.c

@@ -266,8 +266,7 @@ void sysctl_head_put(struct ctl_table_header *head)
 
 static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
 {
-	if (!head)
-		BUG();
+	BUG_ON(!head);
 	spin_lock(&sysctl_lock);
 	if (!use_table(head))
 		head = ERR_PTR(-ENOENT);