doc: Update OpenSDA document for flashing with jlink
doc: Update OpenSDA document for flashing with jlink

Flashing support was added to the jlink runner in commit
9f57d11d9b54db77c7deecf03a94894c097bb7d2, but the OpenSDA document
wasn't updated accordingly. Update it now.

Signed-off-by: Maureen Helm <87a696db5547fa477bda9f9e0f00013c839c14d3@nxp.com>

nashif/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,explora26/zephyr,nashif/zephyr,ldts/zephyr,nashif/zephyr,Vudentz/zephyr,ldts/zephyr,galak/zephyr,punitvara/zephyr,explora26/zephyr,kraj/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,punitvara/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,kraj/zephyr,ldts/zephyr,galak/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,explora26/zephyr,galak/zephyr,explora26/zephyr,ldts/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,finikorg/zephyr,nashif/zephyr,kraj/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,kraj/zephyr