staging: echo.c: fix memory leakage

we should check the return value of calling function fir16_create(): a NULL
value means the memory allocation fails.

this patch also cleans up the error handling in function function oslec_create()

Signed-off-by: Cong Ding <dinggnu@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>