Revert "[release-branch.go1.10] cmd/compile/internal/gc: OMUL should be evaluated when using soft-float"

This reverts commit d74e69c.

Reason for revert: this fix has been backported to 1.11, and that makes
it ineligible for backport to 1.10, since upgrading to 1.11 is a valid
workaround according to https://github.com/golang/go/wiki/MinorReleases.

Also, this triggers a bug on Wasm that would require a backport of
CL 149965, too.

Updates #28688
Updates #28959

Change-Id: I4e56554ea27b5db83bdb1e9d2103dd24e3da8cfc
Reviewed-on: https://go-review.googlesource.com/c/154297
Reviewed-by: Cherry Zhang <[email protected]>
Run-TryBot: Cherry Zhang <[email protected]>

Author: FiloSottile

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

@@ -1168,7 +1168,7 @@ func calcHasCall(n *Node) bool {
 
 	// When using soft-float, these ops might be rewritten to function calls
 	// so we ensure they are evaluated first.
-	case OADD, OSUB, OMINUS, OMUL:
+	case OADD, OSUB, OMINUS:
 		if thearch.SoftFloat && (isFloat[n.Type.Etype] || isComplex[n.Type.Etype]) {
 			return true
 		}