boards: hsdk: let mdb runner connect cores according to configuration
boards: hsdk: let mdb runner connect cores according to configuration

let mdd runner connect connect cores according to CONFIG_MP_NUM_CPUS,
e.g.
   * CONFIG_MP_NUM_CPUS = 2, just connect 2 cores
   * CONFIG_MP_NUM_CPUS = 1, just connect 1 core
   * CONFIG_MP_NUM_CPUS = 4, connect all 4 cores

Signed-off-by: Wayne Ren <d5c6d7c4aa45e53f819f17870783d153a32ba7d0@synopsys.com>

galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,galak/zephyr