Currently cpu.h defines a mixture of functions and types needed by
the rest of QEMU and those needed only by files within target-arm/.
Split the latter out into a new header so they aren't needlessly
exposed further than required.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>