helper/log: remove dead code in log_forward()

helper/log: remove dead code in log_forward()

Commit f1be0e6af2e204805a8bc2e8cadf828b9fa46c98 ("HELPER/LOG:
review unused symbols") removed a set of unused functions and,
as consequence, there is no code anymore that sets the variable
"log_forward_count". But, the commit above did not removed the
code (now dead) that depends on "log_forward_count" set.

Remove the code dependant on "log_forward_count" set and the
variable itself.

Change-Id: I6efe93d1dccbe13c409c5bc55ba47a2684c0e3ac
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/4779
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>