slub: fix leak of 'name' in sysfs_slab_add

The failure paths of sysfs_slab_add don't release the allocation of
'name' made by create_unique_id() a few lines above the context of the
diff below.  Create a common exit path to make it more obvious what
needs freeing.

[vdavydov@parallels.com: free the name only if !unmergeable]
Signed-off-by: Dave Jones <davej@fedoraproject.org>
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>