vk: Fix 3DSTATE_WM_DEPTH_STENCIL for gen8

This packet is a different size on gen8 and we hit an assertion when we
try to merge a gen9 size dword array from the pipeline with the gen8
sized array we create from dynamic state.

Use a static assert in the merge macro and fix this issue by using different
wm_depth_stencil arrays on gen8 and gen9.
3 files changed