arm: ls102xa: Select ge2_clk125 for eTSEC clock muxing

EC1 pins in RCW can be selected as RGMII1, GPIO3, CAN1/2, FTM1 or
SAI1/2. There is a bug that EC3 RGMII could not work when selecting EC1
as other functionality except RGMII. The workaround is to select
ge2_clk125 for eTSEC clock muxing in register SCFG_ETSECCMCR.

Signed-off-by: Alison Wang <alison.wang@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>