sanitycheck: Allow custom arguments for west-flash
sanitycheck: Allow custom arguments for west-flash

This allows you to use west to flash the device and pass custom
arguments to the flash command.

Signed-off-by: Andy Doan <e3579b1e47f273529f0f929453e939a68ede9fd1@foundries.io>

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