crypto/sha1, crypto/sha256: fix typo fisrt -> first

Change-Id: I9bb7568ca16b420254796eb38dfb86c5ca3399d7
Reviewed-on: https://go-review.googlesource.com/77890Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/crypto/sha1/sha1block_arm64.s

@@ -21,7 +21,7 @@
 
 // func sha1block(h []uint32, p []byte, k []uint32)
 TEXT ·sha1block(SB),NOSPLIT,$0
-	MOVD	h_base+0(FP), R0                             // hash value fisrt address
+	MOVD	h_base+0(FP), R0                             // hash value first address
 	MOVD	p_base+24(FP), R1                            // message first address
 	MOVD	k_base+48(FP), R2                            // k constants first address
 	MOVD	p_len+32(FP), R3                             // message length

src/crypto/sha256/sha256block_arm64.s

@@ -11,7 +11,7 @@
 
 // func sha256block(h []uint32, p []byte, k []uint32)
 TEXT ·sha256block(SB),NOSPLIT,$0
-	MOVD	h_base+0(FP), R0                           // Hash value fisrt address
+	MOVD	h_base+0(FP), R0                           // Hash value first address
 	MOVD	p_base+24(FP), R1                          // message first address
 	MOVD	k_base+48(FP), R2                          // k constants first address
 	MOVD	p_len+32(FP), R3                           // message length