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 <[e-mail]>"
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/lustre/lustre/obdecho/echo_client.c

···
 	.o_disconnect  = echo_client_disconnect
 };
 
-int echo_client_init(void)
+static int echo_client_init(void)
 {
 	int rc;
 
···
 	return rc;
 }
 
-void echo_client_exit(void)
+static void echo_client_exit(void)
 {
 	class_unregister_type(LUSTRE_ECHO_CLIENT_NAME);
 	lu_kmem_fini(echo_caches);