Revert "rtl8139: do the network/host communication only in normal operating mode"

This reverts commit ff71f2e8cacefae99179993204172bc65e4303df. This is because
the linux 8139cp driver would leave the card in "Config Register Write Enable"
mode after the eeprom were read or write ( which is unexpected in the spec
). Also a physical 8139 card can still DMA into host memory in modes other than
Normal mode, so we need revert this commit to align with the behavior of
physical card.

The issue of 8139cp driver should be fixed in linux seperately.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
