ARM: dts: imx: name the interrupts for the fec ethernet driver

imx7s/imx7d has the ptp interrupt newly added as well.

For imx7, "int0" is the interrupt for queue 0 and ENET_MII
"int1" is for queue 1
"int2" is for queue 2

For imx6sx, "int0" handles all 3 queues and ENET_MII

And of course, the "pps" interrupt is for the PTP_CLOCK_PPS interrupts
This will help document what each interrupt does.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>