vfs: workaround gcc <4.6 build error in link_path_walk()

Commit d6bb3e9075 ("vfs: simplify and shrink stack frame of
link_path_walk()") introduced build problems with GCC versions older
than 4.6 due to the initialisation of a member of an anonymous union in
struct qstr without enclosing braces.

This hits GCC bug 10676 [1] (which was fixed in GCC 4.6 by [2]), and
causes the following build error:

  fs/namei.c: In function 'link_path_walk':
  fs/namei.c:1778: error: unknown field 'hash_len' specified in initializer

This is worked around by adding explicit braces.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=10676
[2] https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=159206

Fixes: d6bb3e9075 (vfs: simplify and shrink stack frame of link_path_walk())
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-metag@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/namei.c

@@ -1775,7 +1775,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
 			struct dentry *parent = nd->path.dentry;
 			nd->flags &= ~LOOKUP_JUMPED;
 			if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
-				struct qstr this = { .hash_len = hash_len, .name = name };
+				struct qstr this = { { .hash_len = hash_len }, .name = name };
 				err = parent->d_op->d_hash(parent, &this);
 				if (err < 0)
 					break;