llvmpipe: enable z32s8x24 format

Now that we can handle it both for sampling and as depth/stencil enable it.
Passes nearly all additional piglit tests which are now performed, with two
exceptions (one being a framebuffer blit which fails for all other formats
including stencil too as we don't support stencil blits, the other reporting
a unexpected GL error so doesn't look to be llvmpipe's fault).

src/gallium/drivers/llvmpipe/lp_screen.c

@@ -363,12 +363,6 @@ llvmpipe_is_format_supported( struct pipe_screen *_screen,
          return FALSE;
    }
 
-   /* TODO: Support Z32_FLOAT_S8X24_UINT. See lp_bld_depth.c. */
-   if (format_desc->colorspace == UTIL_FORMAT_COLORSPACE_ZS &&
-       format_desc->block.bits > 32) {
-      return FALSE;
-   }
-
    if (bind & PIPE_BIND_DEPTH_STENCIL) {
       if (format_desc->layout != UTIL_FORMAT_LAYOUT_PLAIN)
          return FALSE;