arch: arc: fix the bug of "wait for switch" sychronization
arch: arc: fix the bug of "wait for switch" sychronization

after applying commit 3235451880, arc's arch_switch also need's
corresponding fix.

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

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