video_device: fix uninitialized variable warning

[eightycc]

Describe the PR
Fixes may be used uninitialized compiler warning for variable interval_ms when building at optimization level -Og. Compiler is GCC 13.2.

Additional context

../../lib/tinyusb/src/class/video/video_device.c: In function '_negotiate_streaming_parameters':
../../lib/tinyusb/src/class/video/video_device.c:578:36: error: 'interval_ms' may be used uninitialized [-Werror=maybe-uninitialized]
  578 |         payload_size = (frame_size + interval_ms - 1) / interval_ms + 2;
      |                         ~~~~~~~~~~~^~~~~~~~~~~~~
../../lib/tinyusb/src/class/video/video_device.c:530:29: note: 'interval_ms' was declared here
  530 |     uint_fast32_t interval, interval_ms;
      |                             ^~~~~~~~~~~

[hathach]

look good, thank you