usb: gadget: uvc: Missing files for configfs interface

commit c8cd7510 upstream.

Commit 76e0da34 ("usb-gadget/uvc: use per-attribute show and store
methods") caused a stringification of an undefined macro argument "aname",
so three UVC parameters (streaming_interval, streaming_maxpacket and
streaming_maxburst) were named "aname".

Add the definition of "aname" to the main macro and name the filenames as
originaly intended.

Signed-off-by: Petr Cvek <petr.cvek@tul.cz>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>