ptp: idt82p33: optimize _idt82p33_adjfine

Use div_s64 so that the neg_adj is not needed.
Signed-off-by: Min Li <min.li.xe@renesas.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Link: https://lore.kernel.org/r/1604634729-24960-3-git-send-email-min.li.xe@renesas.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/ptp/ptp_idt82p33.c

@@ -320,7 +320,6 @@ static int _idt82p33_adjfine(struct idt82p33_channel *channel, long scaled_ppm)
 {
 	struct idt82p33 *idt82p33 = channel->idt82p33;
 	unsigned char buf[5] = {0};
-	int neg_adj = 0;
 	int err, i;
 	s64 fcw;
 
@@ -340,16 +339,9 @@ static int _idt82p33_adjfine(struct idt82p33_channel *channel, long scaled_ppm)
 	 * FCW = -------------
 	 *         168 * 2^4
 	 */
-	if (scaled_ppm < 0) {
-		neg_adj = 1;
-		scaled_ppm = -scaled_ppm;
-	}
 
 	fcw = scaled_ppm * 244140625ULL;
-	fcw = div_u64(fcw, 2688);
-
-	if (neg_adj)
-		fcw = -fcw;
+	fcw = div_s64(fcw, 2688);
 
 	for (i = 0; i < 5; i++) {
 		buf[i] = fcw & 0xff;