radv: add a pointer to radv_shader_binary in radv_shader

radv: add a pointer to radv_shader_binary in radv_shader

With GPL, we will have to keep the shader binary in the library for
uploading it later, so it's easier to have a pointer in radv_shader.
The shader binary will be freed when the library is destroyed.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18515>