r8169: remove non-NAPI context invocation of rtl8169_rx_interrupt.

Invocation of rtl8169_rx_interrupt from rtl8169_reset_task was originally
intended to retrieve as much packets as possible from the rx ring when a
reset was needed. Nowadays rtl8169_reset_task is only scheduled, with
some delay
a. from the tx timeout watchdog
b. when resuming
c. from rtl8169_rx_interrupt itself

It's dubious that the loss of outdated packets will matter much for a)
and b). c) does not need to call itself again.

Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Cc: Realtek linux nic maintainers <nic_swsd@realtek.com>