cmd/link: fix deferreturn location on wasm

On wasm, pcln tables are indexed by "resumption point ID" instead of
by pc offset. When finding a deferreturn call, we must find the
associated resumption point ID for the deferreturn call.

Update #27518
Fixes wasm bug introduced in CL 134637.

Change-Id: I3d178a3f5203a06c0180a1aa2309bfb7f3014f0f
Reviewed-on: https://go-review.googlesource.com/c/139898


Reviewed-by: Cherry Zhang <cherryyz@google.com>