docs: usb: fix reference to nonexistent file in UVC Gadget

Fix a typo in the path of this reference.

Fixes: 094f391 ("docs: usb: Add documentation for the UVC Gadget")
Cc: Daniel Scally <dan.scally@ideasonboard.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20231022185311.919325-1-vegard.nossum@oracle.com>

Author: vegard

Documentation/usb/gadget_uvc.rst

@@ -126,7 +126,7 @@ might do:
 	create_frame 1920 1080 uncompressed yuyv
 
 The only uncompressed format currently supported is YUYV, which is detailed at
-Documentation/userspace-api/media/v4l/pixfmt-packed.yuv.rst.
+Documentation/userspace-api/media/v4l/pixfmt-packed-yuv.rst.
 
 Color Matching Descriptors
 ~~~~~~~~~~~~~~~~~~~~~~~~~~