rtlwifi: rtl_pci: Fix the bug when inactiveps is enabled.

Reset the driver current tx read/write index to zero when inactiveps
nic out of sync with HW state. Wrong driver tx read/write index will
cause Tx fail.

Signed-off-by: Tsang-Shian Lin <thlin@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Yan-Hsuan Chuang <yhchuang@realtek.com>
Cc: Birming Chiu <birming@realtek.com>
Cc: Shaofu <shaofu@realtek.com>
Cc: Steven Ting <steventing@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>