helper/command: remove command "command type"

helper/command: remove command "command type"

Once the wrapper "ocd_bouncer" is removed (which was the only user
of this command), there is no reason to keep the command any
longer.

Remove it.

This change was part of http://openocd.zylin.com/1815 from Paul
Fertser and has been extracted and rebased to simplify the review.

Change-Id: I979ce1c147babedb44dd77418751133f589f827c
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5084
Tested-by: jenkins