sm501: Use stn_he_p/ldn_he_p instead of switch/case

Instead of open coding op with different sizes using a switch and type
casting it can be written more compactly using stn_he_p/ldn_he_p.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: e2f649cb286f0735a10ec87c1b36a7ae081acb61.1592686588.git.balaton@eik.bme.hu
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/display/sm501.c

@@ -766,17 +766,7 @@ static void sm501_2d_operation(SM501State *s)
             for (y = 0; y < height; y++) {
                 i = (dst_x + (dst_y + y) * dst_pitch) * bypp;
                 for (x = 0; x < width; x++, i += bypp) {
-                    switch (format) {
-                    case 0:
-                        d[i] = ~d[i];
-                        break;
-                    case 1:
-                        *(uint16_t *)&d[i] = ~*(uint16_t *)&d[i];
-                        break;
-                    case 2:
-                        *(uint32_t *)&d[i] = ~*(uint32_t *)&d[i];
-                        break;
-                    }
+                    stn_he_p(&d[i], bypp, ~ldn_he_p(&d[i], bypp));
                 }
             }
         } else {