usb: gadget: uvc: Rename uvc_control_ep

usb: gadget: uvc: Rename uvc_control_ep

The f_uvc code defines an endpoint named "uvc_control_ep" but it
is configured with a non-zero endpoint address and has its
bmAttributes flagged as USB_ENDPOINT_XFER_INT - this cannot be the
VideoControl interface's control endpoint, as the default endpoint
0 is used for that purpose. This is instead the optional interrupt
endpoint that can be contained by a VideoControl interface. There
is also a Class-specific VC Interrupt Endpoint Descriptor and a
SuperSpeed companion descriptor that are also for the VC interface's
interrupt endpoint but are named as though they are for the control
endpoint.

Rename the variables to make that clear.

Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Link: https://lore.kernel.org/r/20230130105045.120886-2-dan.scally@ideasonboard.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>