RDMA/restrack: Un-inline set task implementation

Prepare rdma_restrack_set_task() call to accommodate more
code by moving its implementation from *.h to *.c.

Reviewed-by: Artemy Kovalyov <artemyko@mellanox.com>
Reviewed-by: Yossi Itigin <yosefe@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
diff --git a/include/rdma/restrack.h b/include/rdma/restrack.h
index 9654d33..0bddbbd 100644
--- a/include/rdma/restrack.h
+++ b/include/rdma/restrack.h
@@ -175,14 +175,8 @@
  * @res:  resource entry
  * @task: task struct
  */
-static inline void rdma_restrack_set_task(struct rdma_restrack_entry *res,
-					  struct task_struct *task)
-{
-	if (res->task)
-		put_task_struct(res->task);
-	get_task_struct(task);
-	res->task = task;
-}
+void rdma_restrack_set_task(struct rdma_restrack_entry *res,
+			    struct task_struct *task);
 
 /*
  * Helper functions for rdma drivers when filling out