Fix IPC interface for preparing protocol

Fix IPC interface for preparing protocol

- Requirement:
Client want to send mode information to server with hello message.

- Solution:
Actually, mode information is already set before calling tts_prepare()
function, so client should be able to send mode information within hello
message. However, current code sends mode information through another
IPC method.
This patch changes the hello message interface between server and
client. Through this patch, client can send mode information with hello
message at once.

Change-Id: Ie4c622b48507935d2ba35980fc2b44c4854bdeb8
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>