Fix fps setting and metadata issue

[xzhangxa]

Framerate setting fix patch:

• Fix the wrong assumption of numerator always 1 and framerate overflow;
• Choose the close framerate for current resolution if not exactly match.

Metadata issue fix patch:

Set up per channel DMA buffer for metadata instead of using the original one in tegra_mc_vi. Previously the depth metadata directly uses the DMA buffer in tegra_mc_vi for embedded, then later when enabling the color metadata it still uses the same structure.

[xzhangxa]

Looks good to me. The only comment is, the code will crash if res->n_framerates is of size 0. but we can assume that it's not.

Yeah I was thinking of it too, but the structures are in the same file so we know it's safe. :)

That's a good point, let me amend the patch for a checker here later.