clocksource/drivers/timer-ti-dm: Remove unnecessary NULL check

The "pdata" pointer cannot be NULL because it's checked at the start of
the function.  Delete the check.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YoZM65RFDQAfqV6J@kili


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