st/dri: Reuse stored texture format

When we create a texture, we allocate a pipe_resource for it with a
given format. When we export the texture to an EGLImage, we go look
up what the GL format was and try to re-derive the pipe_format back
again.

Instead of doing that, just immediately reuse the pipe_format for the
image's format.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27709>

src/gallium/frontends/dri/dri_helpers.c

@@ -443,7 +443,7 @@ dri2_create_from_texture(__DRIcontext *context, int target, unsigned texture,
    img->level = level;
    img->layer = depth;
    img->in_fence_fd = -1;
-   img->dri_format = driGLFormatToImageFormat(glimg->TexFormat);
+   img->dri_format = glimg->pt->format;
    img->internal_format = glimg->InternalFormat;
 
    img->loader_private = loaderPrivate;