Big hack to make fast clears work on SKL

For whatever reason it seems that certain formats require the clear
color to be programmed as a normalized integer rather than a float.
This doesn't seem to be mentioned in the specs and I've just
discovered this by trial and error.

I can't work out what is going on with MESA_FORMAT_R8G8B8X8_SRGB so
I've just disabled it. R8G8B8A8_SRGB works fine.

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

@@ -416,6 +416,36 @@ set_fast_clear_color(struct brw_context *brw,
    }
 
    if (brw->gen >= 9) {
+      /* BEGIN HACK
+       *
+       * By experimentation it seems that some formats expect a normalised
+       * integer value rather than a float.
+       *
+       * TODO: Find out why!
+       */
+      int max = 0;
+
+      switch (mt->format) {
+      case MESA_FORMAT_R8G8B8X8_UNORM:
+      case MESA_FORMAT_L_UNORM8:
+      case MESA_FORMAT_I_UNORM8:
+         max = 255;
+         break;
+      case MESA_FORMAT_RGBX_UNORM16:
+      case MESA_FORMAT_I_UNORM16:
+      case MESA_FORMAT_L_UNORM16:
+         max = 65535;
+         break;
+      default:
+         goto no_hack;
+      }
+
+      for (int i = 0; i < 4; i++)
+         override_color.ui[i] = roundf(override_color.f[i] * max);
+
+   no_hack:
+      /* END HACK */
+
       mt->gen9_fast_clear_color = override_color;
    } else {
       mt->fast_clear_color_value = 0;
@@ -586,6 +616,9 @@ brw_meta_fast_clear(struct brw_context *brw, struct gl_framebuffer *fb,
       if (!is_color_fast_clear_compatible(brw, format, &ctx->Color.ClearColor))
          clear_type = REP_CLEAR;
 
+      if (brw->gen >= 9 && irb->mt->format == MESA_FORMAT_R8G8B8X8_SRGB)
+         clear_type = REP_CLEAR;
+
       /* From the SNB PRM (Vol4_Part1):
        *
        *     "Replicated data (Message Type = 111) is only supported when