[dev.regabi] cmd/compile: cleanup callTargetLSym

Now that TailCallStmt carries an *ir.Name instead of a *types.Sym,
callTargetLSym can be similarly updated to take the target function as
an *ir.Name.

This inches us closer towards being able to move Linksym and other
properties from *types.Sym to *ir.Name, where they belong.

Passes toolstash -cmp w/ -gcflags=all=-abiwrap.

Change-Id: I091da290751970eba8ed0438f66d6cca88b665a8
Reviewed-on: https://go-review.googlesource.com/c/go/+/284228


Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>