staging/lustre/osc: extern declare osc_caches in a header

This avoids frowned upon extern in the C file, and also
shuts down a sparse warning of
drivers/staging/lustre/lustre/osc/osc_dev.c:55:22: warning: symbol 'osc_caches' was not declared. Should it be static?
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/osc/osc_internal.h

@@ -181,6 +181,8 @@ static inline struct osc_device *obd2osc_dev(const struct obd_device *d)
 	return container_of0(d->obd_lu_dev, struct osc_device, od_cl.cd_lu_dev);
 }
 
+extern struct lu_kmem_descr osc_caches[];
+
 extern struct kmem_cache *osc_quota_kmem;
 struct osc_quota_info {
 	/** linkage for quota hash table */

drivers/staging/lustre/lustre/osc/osc_request.c

@@ -2766,8 +2766,6 @@ static struct obd_ops osc_obd_ops = {
 	.quotactl       = osc_quotactl,
 };
 
-extern struct lu_kmem_descr osc_caches[];
-
 static int __init osc_init(void)
 {
 	struct lprocfs_static_vars lvars = { NULL };