ARM: dts: ls1021a: Add the eTSEC controller nodes

Add basic support for all the eTSEC controllers on the
ls1021a SoC.  Second interrupt group register blocks
and their corresponding Rx/Tx/Err interrupt sources are
included as well for each eTSEC node.

Signed-off-by: Alison Wang <alison.wang@freescale.com>
Signed-off-by: Claudiu Manoil <claudiu.manoil@freescale.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>