os/svcall: Fix TZ context handling issue
os/svcall: Fix TZ context handling issue

TZ context is freed but not updated in the task tcb. This will lead
to reuse of old freed context. So, we set the tz_context in tcb to
NULL.

Signed-off-by: Kishore S N <33058dcca7ce956a91a61ef5ae8fb790ece75b5f@samsung.com>

sunghan-chang/TizenRT,junmin-kim/TizenRT,Samsung/TizenRT,junmin-kim/TizenRT,jeongarmy/TizenRT,an4967/TizenRT,Samsung/TizenRT,jeongarmy/TizenRT,sunghan-chang/TizenRT,pillip8282/TizenRT,jeongarmy/TizenRT,an4967/TizenRT,jsdosa/TizenRT,pillip8282/TizenRT,jeongchanKim/TizenRT,Samsung/TizenRT,jeongchanKim/TizenRT,jeongchanKim/TizenRT,junmin-kim/TizenRT,jsdosa/TizenRT,an4967/TizenRT,jeongarmy/TizenRT,sunghan-chang/TizenRT,pillip8282/TizenRT,jsdosa/TizenRT,an4967/TizenRT,jeongchanKim/TizenRT,sunghan-chang/TizenRT,an4967/TizenRT,jsdosa/TizenRT,sunghan-chang/TizenRT,jeongchanKim/TizenRT,jeongarmy/TizenRT,Samsung/TizenRT,jeongarmy/TizenRT,sunghan-chang/TizenRT,jsdosa/TizenRT,pillip8282/TizenRT,junmin-kim/TizenRT,jsdosa/TizenRT,junmin-kim/TizenRT,jeongchanKim/TizenRT,pillip8282/TizenRT,jeongchanKim/TizenRT,junmin-kim/TizenRT,pillip8282/TizenRT,jsdosa/TizenRT,junmin-kim/TizenRT,an4967/TizenRT,Samsung/TizenRT,Samsung/TizenRT,jeongarmy/TizenRT,pillip8282/TizenRT,Samsung/TizenRT,sunghan-chang/TizenRT,an4967/TizenRT