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>
diff --git a/ipc/shm.c b/ipc/shm.c
index 554429a..d05f6b5 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -894,8 +894,6 @@
 	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;