It accidentally used the cmd id for the gen7 command and had an
outdated lenght field. Spotted while trying to make sense of an ivb
error_state from mesa 7.11 ...

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

I mistakenly "fixed" a bad decode with

commit 7d0a1d5ebbe2c6aecd96eef94b0af038858a0178
Author: Ben Widawsky <ben@bwidawsk.net>
Date:   Sun Jun 24 20:35:57 2012 -0700

    intel/decode: VERTEX_ELEMENT_STATE, 1 means valid

However the actual fix is just to update the reference file, and
include GEN7 in the decode.

Props to Eric Anholt for putting the test in distcheck, or else I
wouldn't have caught this.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>

This one doesn't have the 3DSTATE_HIER_DEPTH_BUFFER bug that the
previous one did.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

This requires pulling the gen6 3DSTATE_WM out to a function so it
doesn't override gen7's handler.

v2: Fix pasteo in interpreting ZW interpolation (thanks danvet!).

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

This just gets packet name and length in place, with the remainder
unfinished.  I've long since finished the work that got me started
fixing up the decode.

Since CC_STATE_POINTERS for gen6 and 7 are quite different but use the
same opcode, move gen6 out to a helper function too, so we can use a
helper function for gen7.

This puts the error message in a consistent location relative to the
packet, and while I'm here I made the error message a bit more
informative.

Now, most static length packets need to just declare their length in
the table and not worry.