s390/vdso: Fix comment within __arch_chacha20_blocks_nostack()

Fix comment within __arch_chacha20_blocks_nostack() so the comment
reflects what the code is doing.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

Author: hcahca

arch/s390/kernel/vdso64/vgetrandom-chacha.S

@@ -118,13 +118,13 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
 	VSLDB	STATE3,STATE3,STATE3,4
 	brctg	%r0,.Ldoubleround
 
-	/* OUTPUT0 = STATE0 + STATE0 */
+	/* OUTPUT0 = STATE0 + COPY0 */
 	VAF	STATE0,STATE0,COPY0
-	/* OUTPUT1 = STATE1 + STATE1 */
+	/* OUTPUT1 = STATE1 + COPY1 */
 	VAF	STATE1,STATE1,COPY1
-	/* OUTPUT2 = STATE2 + STATE2 */
+	/* OUTPUT2 = STATE2 + COPY2 */
 	VAF	STATE2,STATE2,COPY2
-	/* OUTPUT2 = STATE3 + STATE3 */
+	/* OUTPUT3 = STATE3 + COPY3 */
 	VAF	STATE3,STATE3,COPY3
 
 	/*