cmd/compile: intrinsify functions added to runtime/internal/sys

This restores intrinsic status to functions copied from math/bits
into runtime/internal/sys, as an aid to runtime performance.

Updates #35112.

Change-Id: I41a7d87cf00f1e64d82aa95c5b1000bc128de820
Reviewed-on: https://go-review.googlesource.com/c/go/+/206200
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

Author: dr2chase

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

@@ -3519,6 +3519,11 @@ func init() {
 	alias("runtime/internal/atomic", "CasRel", "runtime/internal/atomic", "Cas", lwatomics...)
 
 	alias("runtime/internal/sys", "Ctz8", "math/bits", "TrailingZeros8", all...)
+	alias("runtime/internal/sys", "TrailingZeros8", "math/bits", "TrailingZeros8", all...)
+	alias("runtime/internal/sys", "TrailingZeros64", "math/bits", "TrailingZeros64", all...)
+	alias("runtime/internal/sys", "Len8", "math/bits", "Len8", all...)
+	alias("runtime/internal/sys", "Len64", "math/bits", "Len64", all...)
+	alias("runtime/internal/sys", "OnesCount64", "math/bits", "OnesCount64", all...)
 
 	/******** math ********/
 	addF("math", "Sqrt",