opp: ti: Use device_get_match_data()

Use preferred device_get_match_data() instead of of_match_device() to
get the driver match data. With this, adjust the includes to explicitly
include the correct headers.

As this driver only does DT based matching, of_match_device() will never
return NULL if we've gotten to probe(). Therefore, the NULL check and
error return for it can be dropped.

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>