Fix arm64 vet issues (#964)

Author: klauspost

s2/decode_arm64.s

@@ -60,7 +60,7 @@
 //
 // The d variable is implicitly R_DST - R_DBASE,  and len(dst)-d is R_DEND - R_DST.
 // The s variable is implicitly R_SRC - R_SBASE, and len(src)-s is R_SEND - R_SRC.
-TEXT ·s2Decode(SB), NOSPLIT, $56-64
+TEXT ·s2Decode(SB), NOSPLIT, $56-56
 	// Initialize R_SRC, R_DST and R_DBASE-R_SEND.
 	MOVD dst_base+0(FP), R_DBASE
 	MOVD dst_len+8(FP), R_DLEN

zstd/internal/xxhash/xxhash_arm64.s

@@ -162,12 +162,12 @@ finalize:
 	MOVD h, ret+24(FP)
 	RET
 
-// func writeBlocks(d *Digest, b []byte) int
+// func writeBlocks(s *Digest, b []byte) int
 TEXT ·writeBlocks(SB), NOSPLIT|NOFRAME, $0-40
 	LDP ·primes+0(SB), (prime1, prime2)
 
 	// Load state. Assume v[1-4] are stored contiguously.
-	MOVD d+0(FP), digest
+	MOVD s+0(FP), digest
 	LDP  0(digest), (v1, v2)
 	LDP  16(digest), (v3, v4)