Revert "cmd/compile: spill output parameters passed in registers as autos"

Revert "cmd/compile: spill output parameters passed in registers as autos"

This reverts commit 8ed438c077d82c4b4662c327dbbdb3c64e7547ca, CL 300749.

Reason for revert: Looks like it crashes on link-register architectures

Change-Id: I0c261df58900008cada3359889d2a87508158447
Reviewed-on: https://go-review.googlesource.com/c/go/+/302053
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>