staging/lustre: clean function declaration in cl_io.c up

We get 1 warning when building kernel with W=1:
drivers/staging/lustre/lustre/obdclass/cl_page.c:488:6: warning: no previous prototype for 'cl_page_disown0' [-Wmissing-prototypes]

In fact, this function is declared in
drivers/staging/lustre/lustre/obdclass/cl_io.c, but should be
removed in a header file. thus can be recognized in other file.

So this patch moves the declaration into
drivers/staging/lustre/lustre/include/cl_object.h.
Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/include/cl_object.h

@@ -2254,6 +2254,8 @@ void cl_page_unassume(const struct lu_env *env,
 		      struct cl_io *io, struct cl_page *pg);
 void cl_page_disown(const struct lu_env *env,
 		    struct cl_io *io, struct cl_page *page);
+void cl_page_disown0(const struct lu_env *env,
+		     struct cl_io *io, struct cl_page *pg);
 int cl_page_is_owned(const struct cl_page *pg, const struct cl_io *io);
 
 /** @} ownership */

drivers/staging/lustre/lustre/obdclass/cl_io.c

@@ -936,8 +936,6 @@ void cl_page_list_splice(struct cl_page_list *list, struct cl_page_list *head)
 }
 EXPORT_SYMBOL(cl_page_list_splice);
 
-void cl_page_disown0(const struct lu_env *env,
-		     struct cl_io *io, struct cl_page *pg);
 
 /**
  * Disowns pages in a queue.