clocksource/drivers/timer-ti-dm: Change to new style declaration

Variable 'dmtimer_ops' was declared const static instead of static const.

../drivers/clocksource/timer-ti-dm.c:899:1: warning: ‘static’ is not at beginning of declaration [-Wold-style-declaration]
 const static struct omap_dm_timer_ops dmtimer_ops = {
 ^~~~~

Signed-off-by: Philippe Mazenauer <philippe.mazenauer@outlook.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>