mesa: short-cut new_state == _NEW_LINE in _mesa_update_state_locked()

mesa: short-cut new_state == _NEW_LINE in _mesa_update_state_locked()

We can skip to the end of _mesa_update_state_locked() if only the
_NEW_LINE flag is set since none of the derived state depends on it
(just like _NEW_CURRENT_ATTRIB).  Note that we still call the
ctx->Driver.UpdateState() function, of course.

v2: use bitmask-based test, per Eric.

Reviewed-by: Eric Anholt <eric@anholt.net>