clocksource/drivers/timer-ti-dm: Simplify register access further

Let's unify register access and use dmtimer_read() and dmtimer_write()
also for the timer revision specific registers like we now do for the
shread registers.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Link: https://lore.kernel.org/r/20220815131250.34603-5-tony@atomide.com


Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>