hw/misc/bcm2835_cprman: add the DSI0HSCK multiplexer

hw/misc/bcm2835_cprman: add the DSI0HSCK multiplexer

This simple mux sits between the PLL channels and the DSI0E and DSI0P
clock muxes. This mux selects between PLLA-DSI0 and PLLD-DSI0 channel
and outputs the selected signal to source number 4 of DSI0E/P clock
muxes. It is controlled by the cm_dsi0hsck register.

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>