vc4: Add support for texture tiling.

This still treats everything as RGBA8888 for the most part, same as
before.  This is a prerequisite for handling other texture formats, since
only RGBA8888 has a raster-layout mode.

src/gallium/drivers/vc4/vc4_screen.c

@@ -302,7 +302,7 @@ vc4_screen_get_shader_param(struct pipe_screen *pscreen, unsigned shader,
         return 0;
 }
 
-uint8_t
+static uint8_t
 vc4_get_texture_format(enum pipe_format format)
 {
         switch (format) {