boards: arm: nucleo_l152re: fix openOCD issue to access bank2
boards: arm: nucleo_l152re: fix openOCD issue to access bank2

There is a bug in OpenOCD which prevent to flash the bank2
of nucleo_l152re: http://openocd.zylin.com/#/c/5829/
Waiting for official fix, here is a workaround.
TODO: To be reverted once official fix is merged and available in
Zephyr.

Signed-off-by: Alexandre Bourdiol <c23cc711c078d3e6bb50b3dc45a1b8842691e59a@st.com>

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