JOE DIFFIE ''Bigger Than the Beatles'' (Epic) This lighthearted tale of an amateur rocker and his shopgirl squeeze is really just a lame device to evoke the names of beloved rock heroes (Beatles, Stones, Eagles, Elvis). The coattail-riding gets hard to take when Diffie launches into a chorus of ''yeh-yeh-yeh-yeah.'' No, no, no, no. C-

