vp9_ethread: modify the cyclic refresh struct

Two members in struct CYCLIC_REFRESH
  int64_t projected_rate_sb;
  int64_t projected_dist_sb;
are updated at the superblock level, which makes them shared data
in the multi-thread situation, and requires extra work to handle
them. However, those values are updated and used immediately, and
therefore can be removed. This patch cleaned up the code and
removed the two members.

Change-Id: I2c6ee4552bf49fb63ce590cdb47f9723974fffb1
Merge "vp9_ethread: modify the cyclic refresh struct"