jtag: adapter: rework adapter related commands

currently we have different types of same command group:
- starting with adapter_*
- starting with interface*
- without adapter or interface prefix.

Since interface name is already used, we can only use "adapter" command
group by keeping old commands as well.

Change-Id: Id0a1cb63a2ea6860c67ae1e7a3a06a37ddf464f4
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-on: http://openocd.zylin.com/4774
Reviewed-by: Marc Schink <dev@zapb.de>
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-by: Oleksij Rempel <linux@rempel-privat.de>