soc: ti: pruss: Remove wrong check against *get_match_data return value
Since the of_device_get_match_data() doesn't return error code, remove
wrong IS_ERR test. Proper check against NULL pointer is already done
later before usage: if (data && data->...).
Additionally, proceeding with empty device data is valid (e.g. in case
of "ti,am3356-pruss").