fix bug in minicpm-v code

[tc-mb]

I found some bugs that caused loss of precision, here is the fix code.

1. The mmproj of minicpm-v has precision issues, I have modified it and re-uploaded hf.
2. The scheme of minicpm-v2.6 has issues, I have fixed it.
3. There is a bug in minicpm-v conversion script, I have fixed it.

[apepkuss]

Is it possible to update README-minicpmv2.6.md along with this PR? It seems outdated. Thanks!

[ngxson]

Optional, but I highly recommend to that that assertion in my comment, so the code is a bit easier to understand for new developers.

[tc-mb]

Optional, but I highly recommend to that that assertion in my comment, so the code is a bit easier to understand for new developers.

Yes, I think what you said is better. But I think this PR is a simple fix merge. I want to merge it as soon as possible so that everyone can use the minicpm-v model with better effects.

I want to optimize this directly in your refactoring. Do you think this is better?

[tc-mb]

Is it possible to update README-minicpmv2.6.md along with this PR? It seems outdated. Thanks!

sure, I will update it.

[tc-mb]

@ggerganov @ngxson
This is a small update to fix minicpmv bugs. The changes are very minor and the accuracy has been verified.
It may not have been noticed, so it has not been merged. Please see if it can be merged directly. thx ^_^