staging: lustre: echo_client: fix sparse declaration warnings

Fixes the following sparse warnings:

drivers/staging/lustre/lustre/obdecho/echo_client.c:2142:5: warning: symbol 'echo_client_init' was not declared. Should it be static?
drivers/staging/lustre/lustre/obdecho/echo_client.c:2157:6: warning: symbol 'echo_client_exit' was not declared. Should it be static?

Signed-off-by: Zoltán Lajos Kis <zoltan.lajos.kis@gmail.com&gt;">
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>