helper/command: make script_debug() static

helper/command: make script_debug() static

Now that all commands are executed through the common handler
command_unknown(), the message about command execution is logged
by command_unknown(). There is no need, for "native" commands
(.jim_handler) at root level to log the message (again) by itself.

Remove calls to script_debug() apart from command_unknown().
Make script_debug() static as only used in command.c.

Change-Id: I9b2728b69e7643d6121c4b35a96bc825bcb5488d
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5676
Tested-by: jenkins
Reviewed-by: Oleksij Rempel <linux@rempel-privat.de>