Fix ticket #209: condition to parse pcm_flag

When qtbtt_dual_tree_intra_flag = 1, cu.lwidth() and cu.lheight() are equal to 0 when treeType == DUAL_TREE_CHROMA. This causes pcm_flag to not be parsed in this case, whereas the specification tells the contrary.

This patch revert the part of d466acdb which bring the issue.