Had upper endoscopy done that said that all the biopsies were within normal limits. does this mean no gastritis?

Yes: Normally gastritis is one of the conditions that is best diagnosed by endoscopy. Usually your doctor would tell you right after the endoscopy as well if he/she saw any gastritis and the biopsy would show inflammation. You should ask specifically but most likely you don't have gastritis.

Yes: it means that was nothing abnormal (like inflammation) detected on the biopsies.