monitor: use DIV_ROUND_UP

I used the clang-tidy qemu-round check to generate the fix:
https://github.com/elmarco/clang-tools-extraSigned-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NRichard Henderson <rth@twiddle.net>

monitor.c

@@ -1349,7 +1349,7 @@ static void memory_dump(Monitor *mon, int count, int format, int wsize,
 
     switch(format) {
     case 'o':
-        max_digits = (wsize * 8 + 2) / 3;
+        max_digits = DIV_ROUND_UP(wsize * 8, 3);
         break;
     default:
     case 'x':
@@ -1357,7 +1357,7 @@ static void memory_dump(Monitor *mon, int count, int format, int wsize,
         break;
     case 'u':
     case 'd':
-        max_digits = (wsize * 8 * 10 + 32) / 33;
+        max_digits = DIV_ROUND_UP(wsize * 8 * 10, 33);
         break;
     case 'c':
         wsize = 1;