Fix bug in intra mode rd penalty.

Fix bug in intra mode rd penalty.

The intra mode rd penalty was implemented as a rate penalty.
Code was added to scale the penalty according to block size but
this was not done correctly for the SB level or sub 8x8.

The code did a weird double scaling in regard to bit depth that
has been removed. Given that it is a rate penalty the bit depth
should not matter.

This bug fix improves average metrics  on our standard test
sets by about 0.1%

Change-Id: I7cf81b66aad0cda389fe234f47beba01c7493b1e