powerpc/86xx: Add support for Emerson/Artesyn MVME7100

Add support for the Artesyn MVME7100 Single Board Computer.

The MVME7100 is a 6U form factor VME64 computer with:

    - A two e600 cores Freescale MPC8641D CPU
    - 2 GB of DDR2 onboard memory
    - Four Gigabit Ethernets
    - Five 16550 compatible UARTs
    - One USB 2.0 port
    - Two PCI/PCI eXpress Mezzanine Card (PMC/XMC) Slots
    - A DS1375 Real Time Clock (RTC)
    - 512 KB of Non-Volatile Memory (NVRAM)
    - Two 64 KB EEPROMs
    - 128 MB NOR and 4/8 GB NAND Flash

This patch is based on linux-4.7-rc1 and has been only boot tested.

Limitations:
    This patch covers only models 171 and 173
    No plans to support CPLD timers

Know issues:
    All four PHYs work in polling mode

Configuration is missing for:
    PCI IDSEL and PCI Interrupt definition

Support is missing for:
    Cache and memory controllers (which are very similar to the 85xx ones
        but right now I don't know if we can re-use their support)
    Watchdog, USB, NVRAM, NOR, NAND, EEPROMs, VME, PMC/XMC and RTC

Signed-off-by: Alessio Igor Bogani <alessio.bogani@elettra.eu>
Signed-off-by: Scott Wood <oss@buserror.net>

arch/powerpc/boot/motload-head.S

@@ -0,0 +1,11 @@
+#include "ppc_asm.h"
+
+	.text
+	.globl _zimage_start
+_zimage_start:
+	mfmsr   r10
+	rlwinm  r10,r10,0,~(1<<15)        /* Clear MSR_EE */
+	sync
+	mtmsr   r10
+	isync
+	b	_zimage_start_lib