clocksource/drivers/timer-ti-dm: Select TIMER_OF

clocksource/drivers/timer-ti-dm: Select TIMER_OF

When building OMAP_DM_TIMER without TIMER_OF, there are orphan sections
due to the use of TIMER_OF_DELCARE() without CONFIG_TIMER_OF. Select
CONFIG_TIMER_OF when enaling OMAP_DM_TIMER:

arm-linux-gnueabi-ld: warning: orphan section `__timer_of_table' from `drivers/clocksource/timer-ti-dm-systimer.o' being placed in section `__timer_of_table'

Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/202108282255.tkdt4ani-lkp@intel.com/
Cc: Tony Lindgren <tony@atomide.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Keerthy <j-keerthy@ti.com>
Cc: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Cc: Ladislav Michl <ladis@linux-mips.org>
Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: linux-omap@vger.kernel.org
Fixes: 52762fbd1c47 ("clocksource/drivers/timer-ti-dm: Add clockevent and clocksource support")
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20210828175747.3777891-1-keescook@chromium.org
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>