drivers/bluetooth: ipm_stm32: Wake up C2 at init
drivers/bluetooth: ipm_stm32: Wake up C2 at init

When C2 is powered on, flash erase/write operation requires C1
to share a flash mutex with C2. This can only be done if IPM
communication is set up (SHCI).
Instead of configuring C2 (BLE controller) at on ble open,
do it at driver start up.
This allows flash operations before ble_open.

Signed-off-by: Erwan Gouriou <de4d967452b83bb0e37525652734e7d9163b6a4c@linaro.org>

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