clocksource/drivers/timer-ti-dm: Make timer_get_irq static

We can make timer_get_irq() static as noted by Janusz. It is only used by
omap_rproc_get_timer_irq() via platform data.

Reported-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20221028103604.40385-1-tony@atomide.com


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