flash/stm32l4x: STM32L5 support programming when TZEN=1 and RDP=0xAA

flash/stm32l4x: STM32L5 support programming when TZEN=1 and RDP=0xAA

STM32L5 flash memory is aliased to 0x0C000000, this address mapping
is used for secure applications. (0x08000000 for non-secure)

this change allows the programming of secure and non-secure flash
when trustzone is enabled and RDP level is 0

Change-Id: I89d1f1b5d493cf01a142ca4dbfef5a3731cab96e
Signed-off-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/5936
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-by: Oleksij Rempel <linux@rempel-privat.de>