Revert "r8152: napi hangup fix after disconnect"

This reverts commit 0ee1f473.

The commit 0ee1f473 ("r8152: napi hangup fix after
disconnect") adds a check about RTL8152_UNPLUG to determine
if calling napi_disable() is invalid in rtl8152_close(),
when rtl8152_disconnect() is called. This avoids to use
napi_disable() after calling netif_napi_del().

Howver, commit ffa9fec3 ("r8152: set RTL8152_UNPLUG
only for real disconnection") causes that RTL8152_UNPLUG
is not always set when calling rtl8152_disconnect().
Therefore, I have to revert commit 0ee1f473

 ("r8152:
napi hangup fix after disconnect"), first. And submit
another patch to fix it.

Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>