usb: musb: remove dead code from procfs

When removing the procfs file, I forgot to remove some
code that created and removed that file. Here's a patch
to fix it. Ideally this patch will be melded into the patch
removing the procfs file, don't know if it's possible still.

Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>