i965/tex: add missing include

i965/tex: add missing include

src/mesa/drivers/dri/i965/intel_tex.h:52:40: warning: ‘enum intel_miptree_create_flags’ declared inside parameter list will not be visible outside of this definition or declaration
                 enum intel_miptree_create_flags flags);
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes: cadcd89278edcda8aba2 "i965/tex: Change the flags type on
                             create_for_teximage"
Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>