1000BASE-KX(1G-KX) uses SGMII protocol but the serdes lane runs in 1G-KX
mode. By default, the lane runs in SGMII mode, when a MAC uses a lane
in 1G-KX mode, corresponding bit in PCCR1 for the lane needs to be set,
and needs to fixup dtb accordingly for kernel to do proper initialization.

Hwconfig "fsl_1gkx" is used to indicate a MAC runs in 1G-KX mode, FM1 MAC
1/2/5/6/9/10 are available for 1G-KX, MAC 3/4 run in RGMII mode. To set a
MAC runs in 1G-KX mode, set its' corresponding env in "fsl_1gkx",
'fm1_1g1' stands for FM1-MAC1, 'fm1_1g2' stands for FM1-MAC2, etc.

If all MAC 1/2/5/6/9/10 run in 1G-KX mode, the hwconfig should has below
setting:

fsl_1gkx:fm1_1g1,fm1_1g2,fm1_1g5,fm1_1g6,fm1_1g9,fm1_1g10

Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
[York Sun: Fix compiling warning]
Reviewed-by: York Sun <yorksun@freescale.com>