cpu: remove repetitive word

Change-Id: I6dbed409b549ab2cfc862094f19373816b7c0859
Reviewed-on: https://go-review.googlesource.com/c/sys/+/519076
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>

Author: cuishuang

cpu/cpu.go

@@ -38,7 +38,7 @@ var X86 struct {
 	HasAVX512F          bool // Advanced vector extension 512 Foundation Instructions
 	HasAVX512CD         bool // Advanced vector extension 512 Conflict Detection Instructions
 	HasAVX512ER         bool // Advanced vector extension 512 Exponential and Reciprocal Instructions
-	HasAVX512PF         bool // Advanced vector extension 512 Prefetch Instructions Instructions
+	HasAVX512PF         bool // Advanced vector extension 512 Prefetch Instructions
 	HasAVX512VL         bool // Advanced vector extension 512 Vector Length Extensions
 	HasAVX512BW         bool // Advanced vector extension 512 Byte and Word Instructions
 	HasAVX512DQ         bool // Advanced vector extension 512 Doubleword and Quadword Instructions