target-arm: Implement CBAR for Cortex-A57

target-arm: Implement CBAR for Cortex-A57

The Cortex-A57, like most of the other ARM cores, has a CBAR
register which defines the base address of the per-CPU
peripherals. However it has a 64-bit view as well as a
32-bit view; expand the QOM reset-cbar property from UINT32
to UINT64 so this can be specified, and implement the
32-bit and 64-bit views of a 64-bit CBAR.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>