mesa: Silence GCC warning in _mesa_test_texobj_completeness

mesa: Silence GCC warning in _mesa_test_texobj_completeness

main/texobj.c: In function '_mesa_test_texobj_completeness':
main/texobj.c:553:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
main/texobj.c:553:193: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
main/texobj.c:553:254: warning: signed and unsigned type in conditional expression [-Wsign-compare]
main/texobj.c:553:148: warning: signed and unsigned type in conditional expression [-Wsign-compare]

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>