drivers: optee: use flexible-array member instead of zero-length array

Use flexible-array member introduced in C99 instead of zero-length
array. Most of zero-length array was already taken care in previous
patch [1]. Now modified few more cases which were not handled earlier.

[1]. https://patchwork.kernel.org/patch/11394197/

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

drivers/tee/optee/optee_msg.h

@@ -199,7 +199,7 @@ struct optee_msg_arg {
 	u32 num_params;
 
 	/* num_params tells the actual number of element in params */
-	struct optee_msg_param params[0];
+	struct optee_msg_param params[];
 };
 
 /**