Merge branch 'phy-realtek-delays'

Serge Semin says:

====================
net: phy: realtek: Fix RGMII TX/RX-delays initial config of rtl8211(e|f)

It has been discovered that RX/TX delays of rtl8211e ethernet PHY
can be configured via a MDIO register hidden in the extension pages
layout. Particularly the extension page 0xa4 provides a register 0x1c,
which bits 1 and 2 control the described delays. They are used to
implement the "rgmii-{id,rxid,txid}" phy-mode support in patch 1.

The second patch makes sure the rtl8211f TX-delay is configured only
if RGMII interface mode is specified including the rgmii-rxid one.
In other cases (most importantly for NA mode) the delays are supposed
to be preconfigured by some other software or hardware and should be
left as is without any modification. The similar thing is also done
for rtl8211e in the patch 1 of this series.

Changelog v3
- Add this cover-letter.
- Add Andrew' Reviewed-by tag to patch 1.
- Accept RGMII_RXID interface mode for rtl8211f and clear the TX_DELAY
  bit in this case.
- Initialize ret variable with 0 to prevent the "may be used uninitialized"
  warning in patch 1.

Changelog v4
- Rebase onto net-next
====================

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>