ui: 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>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NRichard Henderson <rth@twiddle.net>

ui/cursor.c

@@ -118,7 +118,7 @@ void cursor_put(QEMUCursor *c)
 
 int cursor_get_mono_bpl(QEMUCursor *c)
 {
-    return (c->width + 7) / 8;
+    return DIV_ROUND_UP(c->width, 8);
 }
 
 void cursor_set_mono(QEMUCursor *c,