Revert "blake2s: add loong64 SIMD implementation"

This reverts CL 661215.

Reason for revert: Does not build on 1.23 or 1.24

Fixes #73354.

Change-Id: I90abd8a3dabf5c0d9fd1062de3ba3e78ecb2f2e8
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/664796
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

blake2s/blake2s_ref.go

@@ -2,10 +2,16 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (!amd64 && !386 && !loong64) || !gc || purego
+//go:build (!amd64 && !386) || !gc || purego
 
 package blake2s
 
+var (
+	useSSE4  = false
+	useSSSE3 = false
+	useSSE2  = false
+)
+
 func hashBlocks(h *[8]uint32, c *[2]uint32, flag uint32, blocks []byte) {
 	hashBlocksGeneric(h, c, flag, blocks)
 }