cmd/internal/obj/loong64: fix the error parameters when calling UnspillRegisterArgs
This bug was introduced in CL 648518.
Fixes #73518.
Change-Id: I4988dd0b636c6a6a48d2aa2e2ae868e43f69995a
Reviewed-on: https://go-review.googlesource.com/c/go/+/668475
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Meidan Li <limeidan@loongson.cn> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Keith Randall <khr@google.com>