cmd/compile: remove useless declaration of llit

cmd/compile: remove useless declaration of llit

Accidentally added in https://golang.org/cl/20242.

This is in preparation for transformation by an automated tool.

Passes toolstash -cmp.

Update #14473.

Change-Id: I28c637d220df3ccaa8e368bfbea7282a6e66662e
Reviewed-on: https://go-review.googlesource.com/20402
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>