r600g: make range/block act more like a page table

only allocate the blocks ptr in the range if we ever have one,
otherwise don't bother wasting the memory.

valgrind glxinfo
before:
==967==     in use at exit: 419,754 bytes in 706 blocks
==967==   total heap usage: 3,552 allocs, 2,846 frees, 3,550,131 bytes allocated

after:
==5227==     in use at exit: 419,754 bytes in 706 blocks
==5227==   total heap usage: 3,452 allocs, 2,746 frees, 3,140,531 bytes allocate

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/src/gallium/winsys/r600/drm/r600_priv.h b/src/gallium/winsys/r600/drm/r600_priv.h
index 48c5325..003fca0 100644
--- a/src/gallium/winsys/r600/drm/r600_priv.h
+++ b/src/gallium/winsys/r600/drm/r600_priv.h
@@ -159,7 +159,7 @@
 void r600_context_block_emit_dirty(struct r600_context *ctx, struct r600_block *block);
 void r600_context_dirty_block(struct r600_context *ctx, struct r600_block *block,
 			      int dirty, int index);
-
+int r600_setup_block_table(struct r600_context *ctx);
 void r600_context_reg(struct r600_context *ctx,
 		      unsigned offset, unsigned value,
 		      unsigned mask);