RDMA/efa: Be consistent with success flow return value

The EFA driver is written with success oriented flows in mind, meaning
that functions should mostly end with a return 0 statement.
Error flows return their error value on their own instead of assuming
that the function will return the error at the end.

This commit fixes a bunch of functions that were not aligned with this
behavior.

Reviewed-by: Firas JahJah <firasj@amazon.com>
Reviewed-by: Yossi Leybovich <sleybo@amazon.com>
Signed-off-by: Gal Pressman <galpress@amazon.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/efa/efa_verbs.c

@@ -1594,13 +1594,15 @@ static int __efa_mmap(struct efa_dev *dev, struct efa_ucontext *ucontext,
 		err = -EINVAL;
 	}
 
-	if (err)
+	if (err) {
 		ibdev_dbg(
 			&dev->ibdev,
 			"Couldn't mmap address[%#llx] length[%#llx] mmap_flag[%d] err[%d]\n",
 			entry->address, length, entry->mmap_flag, err);
+		return err;
+	}
 
-	return err;
+	return 0;
 }
 
 int efa_mmap(struct ib_ucontext *ibucontext,