Now no users are setting the frq properties on the CMSDK timer,
dualtimer, watchdog or ARMSSE SoC devices, we can remove the
properties and the struct fields that back them.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20210128114145.20536-25-peter.maydell@linaro.org
Message-id: 20210121190622.22000-25-peter.maydell@linaro.org