MLK-10384-1 ARM: dts: Add EPDC support on i.MX7D SDB

EPDC can not be used together with ENET1 or ENET2.
For ENET1/2 to work, the pin 'ENET_RST_B' from 74LV595PW should be
HIGH normally. But for EPDC, ENET_RST_B need to be LOW otherwise
the signal 'ENET_EN_B" would be LOW which cause the EPDC signals
and ENET2 signals are not isolated by SN74AVC16T245DGGR.

en-gpios property is added for this purpose.
And a new DTS will be added to cover this conflict.

Signed-off-by: Robby Cai <r63905@freescale.com>