r8169: differentiate close chipsets in the startup identification message

The driver displays the same 0x18000000 xid for RTL_GIGA_MAC_VER_06
and RTL_GIGA_MAC_VER_05 whereas the former ought to be identified as
0x98000000.

Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Cc: Edward Hsu <edward_hsu@realtek.com.tw>
Signed-off-by: David S. Miller <davem@davemloft.net>