hw/arm/raspi: add a skeleton implementation of the CPRMAN

hw/arm/raspi: add a skeleton implementation of the CPRMAN

The BCM2835 CPRMAN is the clock manager of the SoC. It is composed of a
main oscillator, and several sub-components (PLLs, multiplexers, ...) to
generate the BCM2835 clock tree.

This commit adds a skeleton of the CPRMAN, with a dummy register
read/write implementation. It embeds the main oscillator (xosc) from
which all the clocks will be derived.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Luc Michel <luc@lmichel.fr>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>