powerpc/85xx: Add support for Emerson/Artesyn MVME2500.

Add support for the Artesyn MVME2500 Single Board Computer.

The MVME2500 is a 6U form factor VME64 computer with:

	- A single Freescale QorIQ P2010 CPU
	- 1 GB of DDR3 onboard memory
	- Three Gigabit Ethernets
	- Five 16550 compatible UARTS
	- One USB 2.0 port, one SHDC socket and one SATA connector
	- One PCI/PCI eXpress Mezzanine Card (PMC/XMC) Slot
	- MultiProcessor Interrupt Controller (MPIC)
	- A DS1375T Real Time Clock (RTC) and 512 KB of Non-Volatile Memory
	- Two 64 KB EEPROMs
	- U-Boot in 16 SPI Flash

This patch is based on linux-3.18 and has been boot tested.

Signed-off-by: Alessio Igor Bogani <alessio.bogani@elettra.eu>
Signed-off-by: Scott Wood <scottwood@freescale.com>