clocksource/drivers/timer-milbeaut: Cleanup common register accesses

Aggregate common register accesses into shared functions for
maintainability.

Signed-off-by: Sugaya Taichi <sugaya.taichi@socionext.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

clocksource/drivers/timer-milbeaut: Add shutdown function

Add a shutdown operation to support shutdown timer.

Signed-off-by: Sugaya Taichi <sugaya.taichi@socionext.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

clocksource/drivers/timer-milbeaut: Fix to enable one-shot timer

Fix mlb_set_oneshot_state() to enable one-shot timer.
The function should stop and start a timer, but "start" statement was
dropped. Kick the register to start one-shot timer.

Fixes: b58f28f306db ("clocksource/drivers/timer-milbeaut: Introduce timer for Milbeaut SoCs")
Signed-off-by: Sugaya Taichi <sugaya.taichi@socionext.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

clocksource/drivers/timer-milbeaut: Introduce timer for Milbeaut SoCs

Add timer driver for Milbeaut SoCs series.

The timer has two 32-bit width down counters, one of which is configured
as a clockevent device and the other is configured as a clock source.

Signed-off-by: Sugaya Taichi <sugaya.taichi@socionext.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>