powerpc/T4240QDS/eth: some fix for XFI

XFI is supported on T4QDS-XFI board, which removed slot3, and four LANEs
of serdes2 are routed to a SFP+ cages, which to house fiber cable or
direct attach cable(copper), the copper cable is used to emulate the
10GBASE-KR scenario.

So, for XFI usage, there are two scenarios, one will use fiber cable,
another will use copper cable. For fiber cable, there is NO PHY, while
for copper cable, we need to use internal PHY which exist in Serdes to
do auto-negotiation and link training, which implemented in kernel.
We use hwconfig to define cable type for XFI, and fixup dtb based on the
cable type.

For copper cable, set below env in hwconfig:

fsl_10gkr_copper:<10g_mac_name>

the <10g_mac_name> can be fm1_10g1, fm1_10g2, fm2_10g1, fm2_10g2. The
four <10g_mac_name>s do not have to be coexist in hwconfig. For XFI ports,
if a given 10G port will use the copper cable for 10GBASE-KR, set the
<10g_mac_name> of the port in hwconfig, otherwise, fiber cable will be
assumed to be used for the port.

For ex. if four XFI ports will both use copper cable, the hwconfig
should contain:

fsl_10gkr_copper:fm1_10g1,fm1_10g2,fm2_10g1,fm2_10g2

For fiber cable:

1. give PHY address to a XFI port, otherwise, the XFI ports will not be
available in U-boot, there is no PHY physically for XFI when using fiber
cable, this is just to make U-boot happy and we can use the XFI ports
in U-boot.
2. fixup dtb to use fixed-link in case of fiber cable which has no PHY.
Kernel requests that a MAC must have a PHY or fixed-link.

When using XFI protocol, the MAC 9/10 on FM1 should init as 10G interface.

Change serdes 2 protocol 56 to 55 which has same feature as 56 since 56
is not valid any longer.

Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>