Merge branch 'mediatek-trgmii'

Sean Wang says:

====================
mediatek: add support for RGMII on GMAC0 through TRGMII hardware module

By default, GMAC0 is connected to built-in switch called
MT7530 through the proprietary interface called Turbo RGMII
(TRGMII). TRGMII also supports well for RGMII as generic external
PHY uses but requires some slight changes to the setup of TRGMII
and doesn't have well support on current driver.

So this patchset
1) provides the slight changes of the setup for RGMII can work
   through TRGMII
2) adds additional setting "trgmii" as PHY_INTERFACE_MODE_TRGMII
   about phy-mode on device tree to make GMAC0 distinguish which
   mode it runs
3) changes dynamically source clock, TX/RX delay and interface
   mode on TRGMII for adapting various link

Changes since v1:
- fixed the style of comment which doesn't have a space at
   the beginning and end of comment lines
- add support for phy-mode "trgmii" as PHY_INTERFACE_MODE_TRGMII
   into linux/phy.h
- enhance the Documentation about device tree binding for trgmii
  which is applicable only for GMAC0 which uses fixed-link
====================

Signed-off-by: David S. Miller <davem@davemloft.net>