ARM: dts: realview: support all the RealView EB board variants

The ARM RealView Evaluation Baseboards are basically these:

- The original ARMv5 EB board with an ARM926EJ-S, ARM1136 or
  ARM1176 core tile here described in arm-realview-eb.dts
  no matter which of these core tiles is being used. This
  can be emulated by QEMU "realview-eb" machine, which by
  default will have the ARM926EJ-S core tile.

- The same board with one of three MPCore Core tiles:
  ARM11MPCore, not to be confused with the similar ARM
  PB11MPCore ARM11MPCore test system. This exist in
  two revisions:
  - Revision A modeled in arm-realview-eb-11mp.dts
  - Revision B modeled arm-realview-eb-11mp-revb.dts
    Revision B can be emulated by the QEMU
    "realview-eb-mpcore" machine, but to match the hardware
    also the argument -smp cpus=4 must be passed so that
    it has four CPU cores, like the hardware.

  There is also evidently from the code in the kernel a
  Cortex-A9 core tile for the EB, and this is modeled in
  arm-realview-eb-a9mp.dts based on the kernel boardfile.
  I have not found a user guide for this EB core tile on
  the ARM website and it seems uncommon. It is however
  included for completeness.

Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>