i965: Fix fast depth clear values on Broadwell.

Broadwell's 3DSTATE_CLEAR_PARAMS packet expects a floating point value
regardless of format.  This means we need to stop converting it to
UNORM.

Storing the value as float would make sense, but since we already have a
uint32_t field, this patch continues shoehorning it into that.  In a
sense, this makes mt->depth_clear_value the DWord you emit in the
packet, rather than the clear value itself.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>

src/mesa/drivers/dri/i965/brw_clear.c

@@ -160,7 +160,10 @@ brw_fast_clear_depth(struct gl_context *ctx)
       /* FALLTHROUGH */
 
    default:
-      depth_clear_value = fb->_DepthMax * ctx->Depth.Clear;
+      if (brw->gen >= 8)
+         depth_clear_value = float_as_int(ctx->Depth.Clear);
+      else
+         depth_clear_value = fb->_DepthMax * ctx->Depth.Clear;
       break;
    }