ARM: dts: split RealView EB 11MPCore variants

There used to be two versions of the RealView EB 11MPCore:

- arm-realview-eb-11mp.dts: the most common variant supported by
  QEMU with the revision C core tile
- arm-realview-eb-revb.dts: for the variant with the elder revision
  B core tile.

As it turns out that there are also a few variants of the
baseboard, unrelated to the coretile, and that these can of
course be mounted on top of each other in all permutations, we
create:

- arm-realview-eb-11mp.dts: the most common variant supported by
  QEMU with the pre-revision D baseboard and the revision C core
  tile.
- arm-realview-eb-11mp-bbrevd.dts: the revision D baseboard
  with the common revision C core tile.
- arm-realview-eb-11mp-ctrevb.dts: the pre-revision D baseboard
  with the revision B core tile.
- arm-realview-eb-11mp-bbrevd-ctrevb.dts: the revision D baseboard
  with the revision B core time.

Or as a table:

           | Core tile: C               | Core tile: B
-----------+----------------------------+-----------------------------------
Baseboard: |                            |
pre-D      |arm-realvie-eb-11mp         | arm-realview-eb-11mp-ctrevb
-----------+----------------------------+-----------------------------------
Baseboard: |                            |
D          |arm-realview-eb-11mp-bbrevd | arm-realview-eb-11mp-bbrevd-ctrevb
-----------+----------------------------+-----------------------------------

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>