net/fm: Fix the endian issue to support both endianness platforms

The Frame Manager(FMan) is a big-endian peripheral, so the
registers, internal MURAM and BDs, which are allocated in main
memory and used to communication between core and FMan, should
be accessed in big-endian. The big-endian platforms can access
them directly as the code implemented so far, while for the
little-endian platforms it need to swap the byte-order.

Signed-off-by: Hou Zhiqiang <B48286@freescale.com>
Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: Mingkai Hu <Mingkai.Hu@freescale.com>
Signed-off-by: Gong Qianyu <Qianyu.Gong@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>