To make fec work with devicetree on imx28-evk, partially port following
kernel patch:

|commit a603a2b
|Author: Linus Walleij <linus.walleij@linaro.org>
|Date:   Sat Dec 30 16:26:36 2017 +0100
|
|    gpio: of: Add special quirk to parse regulator flags
|
|    While most GPIOs are indicated to be active low or open drain using
|    their twocell flags, we have legacy regulator bindings to take into
|    account.
|
|    Add a quirk respecting the special boolean active-high and open
|    drain flags when parsing regulator nodes for GPIOs.
|
|    This makes it possible to get rid of duplicated inversion semantics
|    handling in the regulator core and any regulator drivers parsing
|    and handling this separately.
|
|    Unfortunately the old regulator inversion semantics are specified
|    such that the presence or absence of "enable-active-high" solely
|    controls the semantics, so we cannot deprecate this in favor
|    of the phandle-provided inversion flag, instead any such phandle
|    inversion flag provided in the second cell of a GPIO handle must be
|    actively ignored, so we print a warning to contain the situation
|    and make things easy for the users.
|
|    Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>