hfsplus: fix bless ioctl when used with hardlinks

HFS+ doesn't really implement hard links - instead, hardlinks are indicated
by a magic file type which refers to an indirect node in a hidden
directory. The spec indicates that stat() should return the inode number
of the indirect node, but it turns out that this doesn't satisfy the
firmware when it's looking for a bootloader - it wants the catalog ID of
the hardlink file instead. Fix up this case.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>