1. block_rd_txfm() : av1_optimize_b() should not be called
if pvq is enabled.
Setting t_above and t_left is missing when pvq is enabled,
so added.

2. dist_block() : The nextgen2v has new feature of computing
distortion in pixel domain for speed level = 0, 1, where pvq
works incorrectly since it requres the blank destination
buffer (w/o adding predicted pixels) passed to
inverse trasnform function.

Change-Id: Ia0ee426e796781ee56b4503ea425d447cf88ed8c