Some processors (notably A9 within Highbank) define and use the
CP15 configuration base address (CBAR). This is vendor specific
so its best implemented as a CPU property (otherwise we would need
vendor specific child classes for every ARM implementation).

This patch prepares support for converting CBAR reset value to
a CPU property by moving the CP registration out of the CPU
init fn, as registration will need to happen at realize time
to pick up any property updates. The easiest way to do this
is via definition of a new ARM_FEATURE to flag the existence
of the register.
Signed-off-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 9f697ef1e2ee60a3b9ef971a7f3bc3fa6752a9b7.1387160489.git.peter.crosthwaite@xilinx.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>