i965: Make INTEL_DEBUG=bat decode VS/CLIP/GS/SF/WM/CC_STATE on Gen4-5.

i965: Make INTEL_DEBUG=bat decode VS/CLIP/GS/SF/WM/CC_STATE on Gen4-5.

This is something the original decoder did, but I didn't bother with
until now.  I recently had to debug an Ironlake issue, and wanted to
inspect VS_STATE.  So, now it's back.

The other packets in the switch statement are all Gen6/7+, where we
use offsets from dynamic state base address, so we don't need the
gtt_offset subtraction introduced here.  We might want to make a
helper for this hack at some point - perhaps when we introduce the
next occurance.

Acked-by: Jason Ekstrand <jason@jlekstrand.net>