staging: wilc1000: remove return type of Handle_wait_msg_q_empty

This patch changes return type of Handle_wait_msg_q_empty from s32 with void
because return value is not used.

Signed-off-by: Leo Kim <leo.kim@atmel.com>
Signed-off-by: Glen Lee <glen.lee@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>