cmd/link, cmd/internal/objabi: remove R_DWARFFILEREF relocation type
Get rid of the R_DWARFFILEREF relocation type -- we have not used this
relocation for a while now, ever since jfaller's revamp of the DWARF
line table file section in Go 1.15. No change in compiler or linker
functionality; this is purely a dead code cleanup.
Change-Id: I178760c87f3aa79694cfabe7364ca382605c6975
Reviewed-on: https://go-review.googlesource.com/c/go/+/633876 Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>