shm: Remove silly double assignment

Found a silly double assignment of err is do_shmat.  Silly, but good to
clean up the useless code.
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ipc/shm.c

@@ -894,8 +894,6 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
 	if (!sfd)
 		goto out_put_dentry;
 
-	err = -ENOMEM;
-
 	file = alloc_file(path.mnt, path.dentry, f_mode, &shm_file_operations);
 	if (!file)
 		goto out_free;