wl1251: simplify ELP wakeup time calculation

The wakeup time calculation was too complicated, simplify it.
Signed-off-by: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/wl12xx/wl1251_ps.c

@@ -68,7 +68,7 @@ void wl1251_ps_elp_sleep(struct wl1251 *wl)
 
 int wl1251_ps_elp_wakeup(struct wl1251 *wl)
 {
-	unsigned long timeout;
+	unsigned long timeout, start;
 	u32 elp_reg;
 
 	if (!wl->elp)
@@ -76,6 +76,7 @@ int wl1251_ps_elp_wakeup(struct wl1251 *wl)
 
 	wl1251_debug(DEBUG_PSM, "waking up chip from elp");
 
+	start = jiffies;
 	timeout = jiffies + msecs_to_jiffies(WL1251_WAKEUP_TIMEOUT);
 
 	wl1251_write32(wl, HW_ACCESS_ELP_CTRL_REG_ADDR, ELPCTRL_WAKE_UP);
@@ -96,8 +97,7 @@ int wl1251_ps_elp_wakeup(struct wl1251 *wl)
 	}
 
 	wl1251_debug(DEBUG_PSM, "wakeup time: %u ms",
-		     jiffies_to_msecs(jiffies) -
-		     (jiffies_to_msecs(timeout) - WL1251_WAKEUP_TIMEOUT));
+		     jiffies_to_msecs(jiffies - start));
 
 	wl->elp = false;