softpipe: Do not advertise support for L16 and YCBCR formats.

src/gallium/drivers/softpipe/sp_screen.c

@@ -135,6 +135,9 @@ softpipe_is_format_supported( struct pipe_screen *screen,
           target == PIPE_TEXTURE_CUBE);
 
    switch(format) {
+   case PIPE_FORMAT_L16_UNORM:
+   case PIPE_FORMAT_YCBCR_REV:
+   case PIPE_FORMAT_YCBCR:
    case PIPE_FORMAT_DXT1_RGB:
    case PIPE_FORMAT_DXT1_RGBA:
    case PIPE_FORMAT_DXT3_RGBA: