Removed unused typedef to avoid "unused local typedef" warnings.

Fix warnings about unused local typedefs (reported by gcc 4.8).

Signed-off-by: Han Shen  (shenhan@google.com)

Change-Id: I4bccc234f1390daa808d2b309ed112e20c0ac096
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/compat_ioctl.c

@@ -608,7 +608,6 @@ struct serial_struct32 {
 static int serial_struct_ioctl(unsigned fd, unsigned cmd,
 			struct serial_struct32 __user *ss32)
 {
-        typedef struct serial_struct SS;
         typedef struct serial_struct32 SS32;
         int err;
         struct serial_struct ss;