Add the variable selected configuration for SMP debug with rtos hwthread.
Use SMP by default.
Change-Id: I1c37d91688a3ab58d65c15686737892965711adc
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/7242
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>