ethernet: renesas: Use div64_ul instead of do_div

do_div() does a 64-by-32 division. Here the divisor is an
unsigned long which on some platforms is 64 bit wide. So use
div64_ul instead of do_div to avoid a possible truncation.

Eliminate the following coccicheck warning:
./drivers/net/ethernet/renesas/ravb_main.c:2492:1-7: WARNING:
do_div() does a 64-by-32 division, please consider using div64_ul
instead.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Link: https://lore.kernel.org/r/1637228883-100100-1-git-send-email-yang.lee@linux.alibaba.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/renesas/ravb_main.c

@@ -30,8 +30,7 @@
 #include <linux/spinlock.h>
 #include <linux/sys_soc.h>
 #include <linux/reset.h>
-
-#include <asm/div64.h>
+#include <linux/math64.h>
 
 #include "ravb.h"
 
@@ -2488,8 +2487,7 @@ static int ravb_set_gti(struct net_device *ndev)
 	if (!rate)
 		return -EINVAL;
 
-	inc = 1000000000ULL << 20;
-	do_div(inc, rate);
+	inc = div64_ul(1000000000ULL << 20, rate);
 
 	if (inc < GTI_TIV_MIN || inc > GTI_TIV_MAX) {
 		dev_err(dev, "gti.tiv increment 0x%llx is outside the range 0x%x - 0x%x\n",