r8169: don't reset tx ring indexes in rtl8169_tx_clear

In places where the indexes have to be reset, we call
rtl8169_init_ring_indexes() anyway after rtl8169_tx_clear().

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>