i965: Support images with offset aux buffers

Previously our aux buffers (MCS, and HiZ) never had an offset because
they were in their own buffer object. When using the CCS lossless
compression feature, it's desirable to store the data at an offset from
the main framebuffer, ie. share a buffer object. This patch just makes
having an aux offset possible.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Acked-by: Daniel Stone <daniels@collabora.com>

src/mesa/drivers/dri/i965/intel_image.h

@@ -92,6 +92,9 @@ struct __DRIimageRec {
    /** The image was created with EGL_EXT_image_dma_buf_import. */
    bool dma_buf_imported;
 
+   /** The image has some ancillary data associated with it at offset. */
+   uint32_t aux_offset;
+
    /**
     * Provided by EGL_EXT_image_dma_buf_import.
     * \{

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

@@ -575,6 +575,11 @@ create_image_with_modifier(struct intel_screen *screen,
    image->tile_y = I915_TILING_Y;
    image->modifier = modifier;
 
+   if (image->planar_format)
+      assert(image->planar_format->nplanes == 1);
+
+   image->aux_offset = 0; /* y_tiled_height * pitch; */
+
    return true;
 }