i965: Make the param pointer arrays for the WM dynamically sized.

i965: Make the param pointer arrays for the WM dynamically sized.

Saves 26.5MB of wasted memory allocation in the l4d2 demo.

v2: Rebase on compare func change, fix comments.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com> (v1)
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>