clocksource/drivers/timer-ti-dm: Move inline functions to driver for am6

clocksource/drivers/timer-ti-dm: Move inline functions to driver for am6

The __omap_dm_timer_* inline functions in the header are no longer needed
outside the driver, and the header ifdefs prevent the driver working for
ARCH_K3.

Let's move the inline functions to the driver and drop the ifdefs and
drop the unused functions __omap_dm_timer_override_errata() and
__omap_dm_timer_load_start().

Cc: Keerthy <j-keerthy@ti.com>
Cc: Nishanth Menon <nm@ti.com>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20220408101715.43697-2-tony@atomide.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>