r8169: revert "add byte queue limit support".

This reverts commit 036dafa2.

First it appears in bisection, then reverting it solves the usual
netdev watchdog problem for different people. I don't have a proper
fix yet so get rid of it.

Bisected-and-reported-by: Alex Villacís Lasso <a_villacis@palosanto.com>
Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>