[XL] Change in coreboot[main]: lib/jpeg: Replace decoder with Wuffs' implementation

[Nigel Tao (Code Review)]

Attention is currently required from: Martin L Roth, Patrick Georgi, Tim Wawrzynczak.

Nigel Tao has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78271?usp=email )

Change subject: lib/jpeg: Replace decoder with Wuffs' implementation
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Patch Set 2:

(1 comment)

File src/lib/bootsplash.c:

https://review.coreboot.org/c/coreboot/+/78271/comment/84afe43b_f8c5c5d0 :
PS2, Line 29: 	printk(BIOS_DEBUG, "Bootsplash image resolution: %dx%d\n", image_width, image_height);
image_width (and image_height) will remain uninitialized if the `jpeg_fetch_size` input is an invalid JPEG.

You therefore might be printk'ing junk values. More importantly, the junk values may be negative, which will the pass the `image_width > x_resolution` check but your `framebuffer += etc` calculation might wander out of bounds.

One possible fix:

```
int image_width = -1, image_height = -1;
jpeg_fetch_size(jpeg, filesize, &image_width, &image_height);
printk(etc);
if (((unsigned int)image_width > x_resolution) ||
    ((unsigned int)image_height > y_resolution)) {
  // etc
}
```

Another possible fix, if you want to avoid all the subtlety with implicit signed/unsigned int conversions:

```
if ((image_width <= 0) || (image_width > x_resolution) ||
    (image_height <= 0) || (image_height > y_resolution)) {
  // etc
}
```

Another possible fix is to do the `// TODO: return an error` in `jpeg.c`.