flash/stm32l4x: add support of STM32WL5x dual core

flash/stm32l4x: add support of STM32WL5x dual core

according the RM0453, the second core  have a different Flash CR and SR
registers for flash operations (called C2CR and C2SR).
so we need to a different flash_regs than older L4 devices.
@see stm32wl_cpu2_flash_regs

the C2CR register don't contain LOCK and OPTLOCK bits, and this explain
the addition of new register index called STM32_FLASH_CR_WLK_INDEX to
look-up the CR with lock, to be used in locking/unlocking the flash.

note: DBGMCU_IDCODE cannot be read using CPU1 (Cortex-M0+) at AP1,
to solve this read the UID64 (IEEE 64-bit unique device ID register)

Change-Id: Ifb6e291bf97f814f0b9987b2c40f3037959f7af4
Signed-off-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6050
Tested-by: jenkins
Reviewed-by: Oleksij Rempel <linux@rempel-privat.de>