r8169: remove the obsolete and incorrect AMD workaround

This was introduced in commit 6dccd16b "r8169: merge with version
6.001.00 of Realtek's r8169 driver". I did not find the version
6.001.00 online, but in 6.002.00 or any later r8169 from Realtek
this hunk is no longer present.

Also commit 05af2142 "r8169: fix Ethernet Hangup for RTL8110SC
rev d" claims to have fixed this issue otherwise.

The magic compare mask of 0xfffe000 is dubious as it masks
parts of the Reserved part, and parts of the VLAN tag. But this
does not make much sense as the VLAN tag parts are perfectly
valid there. In matter of fact this seems to be triggered with
any VLAN tagged packet as RxVlanTag bit is matched. I would
suspect 0xfffe0000 was intended to test reserved part only.

Finally, this hunk is evil as it can cause more packets to be
handled than what was NAPI quota causing net/core/dev.c:
net_rx_action(): WARN_ON_ONCE(work > weight) to trigger, and
mess up the NAPI state causing device to hang.

As result, any system using VLANs and having high receive
traffic (so that NAPI poll budget limits rtl_rx) would result
in device hang.

Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Acked-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: David S. Miller <davem@davemloft.net>