fm3: fix erase flash fail on using High Level Adapters.

fm3: fix erase flash fail on using High Level Adapters.

This fix can "erase flash" on using High Level Adapters by running algorithm.
Because fm3 flash commands must need true 16-bit memory access,
but High Level Adapters(ST-Link/TI-ICDI) can 8/32bit access only.
Tested on MB9BF618T and MB9AF112K with STLink/V2.

Change-Id: I849a8a8e8ae2b3e77717de04f7522cf718c915d7
Signed-off-by: Nemui Trinomius <nemuisan_kawausogasuki@live.jp>
Reviewed-on: http://openocd.zylin.com/1944
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>