mpc85xx: introduce the kmp204x reference design support

This patch introduces the support for Keymile's kmp204x reference
design. This design is based on Freescale's P2040/P2041 SoC.

The peripherals used by this design are:
- DDR3 RAM with SPD support
- SPI NOR Flash as boot medium
- NAND Flash
- 2 PCIe busses (hosts 1 and 3)
- 3 FMAN Ethernet devices (FMAN1 DTSEC1/2/5)
- 3 Local Bus windows, with one dedicated to the QRIO reset/power mgmt
  FPGA
- 2 HW I2C busses
- last but not least, the mandatory serial port

The board/keymile/kmp204x code is mostly based on Freescale's P2041rdb
support and was changed according to our design (that means essentially
removing what is not present on the designs and a few adaptations).

There is currently only one prototype board that is based on this design
and this patch also introduces it. The board is called kmlion1.

Signed-off-by: Stefan Bigler <stefan.bigler@keymile.com>
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>

kmp204x: update the ENV #define

The comments had to be refined as well as the total size

Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
[York Sun: fix ddr.c]
Acked-by: York Sun <yorksun@freescale.com>