“We wanted to end up where we started,” said Charlotte Caffey, and what she meant was Los Angeles. That’s the city in which Caffey and her bandmates formed the Go-Go’s in 1978, and it’s the place they returned Tuesday night for the final show of a month-long farewell tour at The Greek. True to the economical spirit of the music, the Go-Go’s didn’t drag out this goodbye with long speeches or a corny video montage. From the band’s opener, “Vacation,” to its closer, “Head Over Heels,” it was onstage for less than 90 minutes — and that included two encores.