[dev.regabi] cmd/compile: use *obj.LSym instead of *ir.Name for staticdata functions

Those functions only use (*ir.Name).Linksym(), so just change them to
get an *obj.LSym directly. This helps get rid of un-necessary
validations that their callers have already done.

Passes toolstash -cmp.

For #43737.

Change-Id: Ifd6c2525e472f8e790940bc167665f9d74dd1bc5
Reviewed-on: https://go-review.googlesource.com/c/go/+/284121


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