mesa/es3: Allow unsized depth and depth-stencil formats in ES3
mesa/es3: Allow unsized depth and depth-stencil formats in ES3

They're part of GL_OES_depth_texture_cube_map, and we'll always enable
that extension in ES3 contexts.

Signed-off-by: Ian Romanick <2b237cafb16dc45038e85df6c85e74e6d899eba9@intel.com>
Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>
Reviewed-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>

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