cpu: remove the use of ioutil

A trivial change.

Change-Id: I8121c263d5b8e9d0634d4f38847aff3cb770ef96
Reviewed-on: https://go-review.googlesource.com/c/sys/+/526301
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Kirill Kolyshkin <kolyshkin@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

cpu/hwcap_linux.go

@@ -5,7 +5,7 @@
 package cpu
 
 import (
-	"io/ioutil"
+	"os"
 )
 
 const (
@@ -39,7 +39,7 @@ func readHWCAP() error {
 		return nil
 	}
 
-	buf, err := ioutil.ReadFile(procAuxv)
+	buf, err := os.ReadFile(procAuxv)
 	if err != nil {
 		// e.g. on android /proc/self/auxv is not accessible, so silently
 		// ignore the error and leave Initialized = false. On some