llvmpipe: tweak CMD_BLOCK_MAX and LP_SCENE_MAX_SIZE

We advertise a max texture/surfaces size of 8K x 8K but the old values
for these limits didn't actually allow us to handle that surface size.

For 8K x 8K we'll have 16384 bins.  Each bin needs at least one cmd_block
object which was 2192 bytes in size.  Since 16384 * 2192 exceeded
LP_SCENE_MAX_SIZE we'd silently fail in lp_scene_new_data_block() and not
draw the complete scene.

By reducing CMD_BLOCK_MAX to 29 we get nice 512-byte cmd_blocks.  And
by increasing LP_SCENE_MAX_SIZE to 9 MB we can allocate enough command
blocks for 8K x 8K, plus a few regular data blocks.

Fixes the (improved) piglit fbo-maxsize test.

Note: This is a candidate for the stable branches.

Reviewed-by: José Fonseca <jfonseca@vmware.com>
(cherry picked from commit a31ebdffa0)

src/gallium/drivers/llvmpipe/lp_scene.h

@@ -49,12 +49,18 @@ struct lp_rast_state;
 #define TILES_Y (LP_MAX_HEIGHT / TILE_SIZE)
 
 
-#define CMD_BLOCK_MAX 128
+/* Commands per command block (ideally so sizeof(cmd_block) is a power of
+ * two in size.)
+ */
+#define CMD_BLOCK_MAX 29
+
+/* Bytes per data block.
+ */
 #define DATA_BLOCK_SIZE (64 * 1024)
 
 /* Scene temporary storage is clamped to this size:
  */
-#define LP_SCENE_MAX_SIZE (4*1024*1024)
+#define LP_SCENE_MAX_SIZE (9*1024*1024)
 
 /* The maximum amount of texture storage referenced by a scene is
  * clamped ot this size: