fbo mipmap complete checks

There are upcoming CTS changes where fbo completeness is checked more thoroughly. Fixing this in Mesa side requires these changes so that fbo completeness check will not fail in these tests. Tests are not setting up max mipmap levels, because of this we fall in to situation where fbo is considered incomplete because texture attachment is not mipmap complete.

Fix is to simply define max mipmap level (smaller that driver would calculate) so that we are mipmap complete and thus fbo can be considered complete.