debugfs: Modified default dir of debugfs for debugging UHCI.

Change default debugfs directory as mounting point for debugging
UHCI(Universal Host Controller Interface driver) for USB.

As we all know, We need change default directory for consistency of
debugfs by Greg K-H

Signed-off-by: GeunSik Lim <geunsik.lim@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>