mac80211_hwsim: fix compiler warning on MIPS

The dividend in do_div() is expected to be an unsigned 64-bit integer,
which leads to the following warning when building for 32-bit MIPS:

  drivers/net/wireless/mac80211_hwsim.c: In function 'mac80211_hwsim_set_tsf':
  drivers/net/wireless/mac80211_hwsim.c:664:98: warning: comparison of distinct pointer types lacks a cast [enabled by default]
    data->bcn_delta = do_div(delta, bcn_int);

Since we care about the signedness of delta when adjusting tsf_offset
and bcm_delta, use the absolute value for the division and compare
the two timestamps to determine the sign.
Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/mac80211_hwsim.c

@@ -685,11 +685,16 @@ static void mac80211_hwsim_set_tsf(struct ieee80211_hw *hw,
 	struct mac80211_hwsim_data *data = hw->priv;
 	u64 now = mac80211_hwsim_get_tsf(hw, vif);
 	u32 bcn_int = data->beacon_int;
-	s64 delta = tsf - now;
+	u64 delta = abs64(tsf - now);
 
-	data->tsf_offset += delta;
 	/* adjust after beaconing with new timestamp at old TBTT */
-	data->bcn_delta = do_div(delta, bcn_int);
+	if (tsf > now) {
+		data->tsf_offset += delta;
+		data->bcn_delta = do_div(delta, bcn_int);
+	} else {
+		data->tsf_offset -= delta;
+		data->bcn_delta = -do_div(delta, bcn_int);
+	}
 }
 
 static void mac80211_hwsim_monitor_rx(struct ieee80211_hw *hw,