panfrost: Format fixes

2 fixes related to texture sampling.

The first one is reverting a commit that forced all Z24 textures to be sampled at R32UI textures, which is not incorrect and leads to regressions.

The second one is passing the correct format to panfrost_new_texture(): we were passing the native texture format instead of the sampler format, leading to incorrect behaviour when they don't match. That's needed if we want to reload the ZS buffer (in this case, Z24S8 textures are sampled as r32ui ones and the 'reload ZS' shader takes care of extracting the Z and S components), and was actually the reason for panfrost: Z24 variants should be sampled as R32UI.

/cc @alyssa @icecream95