ubifs: Fix memory leak in do_rename

In the Linux kernel, the following vulnerability has been resolved:

ubifs: Fix memory leak in do_rename

If renaming a file in an encrypted directory, function
fscrypt_setup_filename allocates memory for a file name. This name is
never used, and before returning to the caller the memory for it is not
freed.

When running kmemleak on it we see that it is registered as a leak. The
report below is triggered by a simple program 'rename' that renames a
file in an encrypted directory:

unreferenced object 0xffff888101502840 (size 32):
comm "rename", pid 9404, jiffies 4302582475 (age 435.735s)
backtrace:
__kmem_cache_alloc_node
__kmalloc
fscrypt_setup_filename
do_rename
ubifs_rename
vfs_rename
do_renameat2

To fix this we can remove the call to fscrypt_setup_filename as it's not
needed.