isl: Validate row pitch of stencil surfaces.
Also, silence an obnoxious finishme that started occurring for all
GL applications which use stencil after the i965 ISL conversion.
v2: Check against 3DSTATE_STENCIL_BUFFER's pitch bits when using
separate stencil, and 3DSTATE_DEPTH_BUFFER's bits when using
combined depth-stencil.
Cc: "17.2" <mesa-stable@lists.freedesktop.org>
Reviewed-by:
Jason Ekstrand <jason@jlekstrand.net>