r8169:modify the behavior of function "rtl8168_oob_notify"

In function "rtl8168_oob_notify", using function "rtl_eri_write" to access
eri register 0xe8, instead of using MAC register "ERIDR" and "ERIAR" to
access it.

For using function "rtl_eri_write" in function "rtl8168_oob_notify", need to
move down "rtl8168_oob_notify" related functions under the function
"rtl_eri_write".

Signed-off-by: Chun-Hao Lin <hau@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>