cmd/internal/obj/arm64: add missing operand register in GNU assembly

Fixes #55832

Change-Id: Ib20279d47c1ca9a383a3c85bb41ca4f550bb0a33
GitHub-Last-Rev: 10af77a
GitHub-Pull-Request: #55838
Reviewed-on: https://go-review.googlesource.com/c/go/+/433575
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: hopehook <hopehook@golangcn.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

src/cmd/internal/obj/arm64/doc.go

@@ -13,7 +13,7 @@ using different register names.
 
 Examples:
 
-	ADC R24, R14, R12          <=>     adc x12, x24
+	ADC R24, R14, R12          <=>     adc x12, x14, x24
 	ADDW R26->24, R21, R15     <=>     add w15, w21, w26, asr #24
 	FCMPS F2, F3               <=>     fcmp s3, s2
 	FCMPD F2, F3               <=>     fcmp d3, d2