cmd/internal/obj/wasm: use i64 for large return addr
Use i64 to avoid overflow when getting PC_F from the return addr.
Fixes #73246
Change-Id: I5683dccf7eada4b8536edf53e2e83116a2f6d943
GitHub-Last-Rev:
267d9a1a031868430d0af530de14229ee1ae8609
GitHub-Pull-Request: golang/go#73277
Reviewed-on: https://go-review.googlesource.com/c/go/+/663995
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>