go/printer: use max/min func

go/printer: use max/min func

Change-Id: I2f708bca0c1e26fb63083731927d5d6a51d41690
GitHub-Last-Rev: 27d2000103d64c47b3c07e92f1d0bd16eadaeac2
GitHub-Pull-Request: golang/go#63320
Reviewed-on: https://go-review.googlesource.com/c/go/+/531915
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Keith Randall <khr@golang.org>