llvmpipe: remove the power of two sizeof(struct cmd_block) assertion

It fails on 32-bit systems (I only tested on 64-bit).  Power of two
size isn't required, so just remove the assertion.

Reviewed-by: José Fonseca <jfonseca@vmware.com>

src/gallium/drivers/llvmpipe/lp_scene.c

@@ -76,13 +76,6 @@ lp_scene_create( struct pipe_context *pipe )
       assert(maxCommandBytes < LP_SCENE_MAX_SIZE);
       /* We'll also need space for at least one other data block */
       assert(maxCommandPlusData <= LP_SCENE_MAX_SIZE);
-
-      /* Ideally, the size of a cmd_block object will be a power of two
-       * in order to avoid wasting space when we allocation them from
-       * data blocks (which are power of two also).
-       */
-      assert(sizeof(struct cmd_block) ==
-             util_next_power_of_two(sizeof(struct cmd_block)));
    }
 #endif