panfrost: enable DrawTransformFeedback*
This is needed for ARB_transform_feedback2, which I plan on requiring for ES3. (Since pause/resume is required for ES3, and in fact that's the name of the PIPE_CAP.)
Note that there are no tests in dEQP for this (as DrawTransformFeedback was never exposed in ES), so someone with (access to) the hardware should run the arb_transform_feedback2-draw-auto piglit test.