kernel: wipe TLS when dropping to user mode
kernel: wipe TLS when dropping to user mode

For threads that run in supervisor mode for some time before
synchronously dropping to user mode, re-initialize the TLS
area to prevent leakage of potentially sensitive information.

We did this already for CONFIG_THREAD_USERSPACE_LOCAL_DATA
but not the new CONFIG_THREAD_LOCAL_STORAGE.

Signed-off-by: Andrew Boie <aab045b28152628be6af0e556050d0381fd0a34d@intel.com>

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