r8169: Fix PCI error on system resume

Some r8168 NICs stop working upon system resume:

[  688.051096] r8169 0000:02:00.1 enp2s0f1: rtl_ep_ocp_read_cond == 0 (loop: 10, delay: 10000).
[  688.175131] r8169 0000:02:00.1 enp2s0f1: Link is Down
...
[  691.534611] r8169 0000:02:00.1 enp2s0f1: PCI error (cmd = 0x0407, status_errs = 0x0000)

Not sure if it's related, but those NICs have a BMC device at function
0:
02:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. Realtek RealManage BMC [10ec:816e] (rev 1a)

Trial and error shows that increase the loop wait on
rtl_ep_ocp_read_cond to 30 can eliminate the issue, so let
rtl8168ep_driver_start() to wait a bit longer.

Fixes: e6d6ca6 ("r8169: Add support for another RTL8168FP")
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Reviewed-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Kai-Heng Feng

drivers/net/ethernet/realtek/r8169_main.c

@@ -1211,7 +1211,7 @@ static void rtl8168ep_driver_start(struct rtl8169_private *tp)
 {
 	r8168ep_ocp_write(tp, 0x01, 0x180, OOB_CMD_DRIVER_START);
 	r8168ep_ocp_write(tp, 0x01, 0x30, r8168ep_ocp_read(tp, 0x30) | 0x01);
-	rtl_loop_wait_high(tp, &rtl_ep_ocp_read_cond, 10000, 10);
+	rtl_loop_wait_high(tp, &rtl_ep_ocp_read_cond, 10000, 30);
 }
 
 static void rtl8168_driver_start(struct rtl8169_private *tp)