i965: Allow 8x MSAA on >= 64bpp formats on Gen8+.

See commit 3b0279a69 - this restriction is documented in the "Surface
Format" field of RENDER_SURFACE_STATE.

Looking at newer documentation, this restriction appears to exist on
Haswell, but no longer applies on Gen8+.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>

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

@@ -806,7 +806,8 @@ brw_render_target_supported(struct brw_context *brw,
    /* Under some conditions, MSAA is not supported for formats whose width is
     * more than 64 bits.
     */
-   if (rb->NumSamples > 0 && _mesa_get_format_bytes(format) > 8) {
+   if (brw->gen < 8 &&
+       rb->NumSamples > 0 && _mesa_get_format_bytes(format) > 8) {
       /* Gen6: MSAA on >64 bit formats is unsupported. */
       if (brw->gen <= 6)
          return false;