USB: core: Replace an empty statement with a debug message

USB: core: Replace an empty statement with a debug message

This patch adds a dev_dbg() message to usb_create_sysfs_intf_files().
The message is not expected ever to appear; it's real purpose is to
satisfy the __must_check attribute on device_create_file() without
triggering a compiler warning about an empty statement.

In fact we don't really care if the sysfs attribute file doesn't get
created.  The interface string descriptor is purely informational and
hardly ever present.

Suggested-by: NeilBrown <neilb@suse.de>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.2004221618500.11262-100000@iolanthe.rowland.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>