libhevcenc: pre enc intra cleanup

code associated with pre enc intra processing is cleaned up.
Unreachable code and debug code is removed. Structure members that
are unused or used for debugging purpose are removed. Control
code is simplified. This helps in memory footprint and object size
foot print.

Test: hevcenc -c vid_enc_cfg.txt
Bug: 139400699
Change-Id: I7697b05ea1d470d93bdb9cb14304cb0bfefd8054
15 files changed