freedreno/a6xx: convert draw packet to OUT_PKT()

freedreno/a6xx: convert draw packet to OUT_PKT()

This is one of the hotter pkt7 packets, since it is guaranteed to happen
on every draw.  Switch to OUT_PKT() for less driver overhead in the draw
path.

Slight bit of cheating for using CP_DRAW_INDX_OFFSET_0 for the first
dword in all cases.  Possibly *gen_header.py* could be more clever
and use typedef's in the cases of bitsets like vgt_draw_initiator.
But this works out because it is always the first dword.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4813>