drivers/net/wireless/wl12xx: Use available error codes

Error codes are stored in ret, but the return value is always 0.  Return
ret instead.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@r@
local idexpression x;
constant C;
@@

if (...) { ...
  x = -C
  ... when != x
(
  return <+...x...+>;
|
  return NULL;
|
  return;
|
* return ...;
)
}
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/wl12xx/wl1271_acx.c

@@ -269,7 +269,7 @@ int wl1271_acx_pd_threshold(struct wl1271 *wl)
 
 out:
 	kfree(pd);
-	return 0;
+	return ret;
 }
 
 int wl1271_acx_slot(struct wl1271 *wl, enum acx_slot_type slot_time)