rtlwifi: Don't clear num_rx_inperiod too early

This patch moves the clearing of rtlpriv->link_info.num_rx_inperiod in
rtl_watchdog_wq_callback a few lines down.

This is necessary since it is still used in the "AP off" detection
code block. Moved clearing of rtlpriv->link_info.num_rx_inperiod
as well for consistency.

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>