linux-wandboard

sh: provide generic arch_debugfs_dir.

While sh previously had its own debugfs root, there now exists a
common arch_debugfs_dir prototype, so we switch everything over to
that.  Presumably once more architectures start making use of this
we'll be able to just kill off the stub kdebugfs wrapper.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>