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").

Reported-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>