Revert "cmd/compile: improve generated eq algs for structs containing interfaces"

This reverts commit 1cc7be89a9.

Reason for revert: Undoing to get back to semantics discussed in #8606.

Change-Id: Ib44a2e79cf113b3d15c3546cd8aa6fc27860819e
Reviewed-on: https://go-review.googlesource.com/c/go/+/236146
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/alg.go

@@ -672,14 +672,6 @@ func geneq(t *types.Type) *obj.LSym {
 					eqlen, eqmem := eqstring(p, q)
 					and(eqlen)
 					and(eqmem)
-				case f.Type.IsInterface():
-					p.Type = f.Type
-					p = typecheck(p, ctxExpr)
-					q.Type = f.Type
-					q = typecheck(q, ctxExpr)
-					eqtab, eqdata := eqinterface(p, q)
-					and(eqtab)
-					and(eqdata)
 				default:
 					and(nod(OEQ, p, q))
 				}