MySQL 5.7 Upgradation - Binary log basename
After, discussion with my colleagues, I found that, the log_bin_basename is read only variable and it took the value from the log-bin definition. So I added another variable log-bin, without modifying the default log_bin variable. Now the binary log enabled and basename pointed to the separate directory.

# BINARY LOGGING
#log_bin # This is default
log-bin                       =       /logs/binlog/mysql-bin
log_bin_basename              =       /logs/binlog/mysql-bin
expire_logs_days              =       5
sync-binlog                   =       1