[dev.regabi] cmd/compile: remove unnecessary Name.Sym call

Since the introduction of ir.BasicLit, we no longer create Names
without Syms.

Passes toolstash -cmp.

Change-Id: I82de3fd65455e3756ff56e52febb512c0a2128f2
Reviewed-on: https://go-review.googlesource.com/c/go/+/280512


Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>