Only write OSD to buffer 0 in frame buffer

Change-Id: Icd741b72b92fbe73af37b25506f7ea7f5c8dda99

src/osd.c

@@ -238,7 +238,6 @@ void osd_clear() {
    if (active) {
       memset(buffer, 0, sizeof(buffer));
       osd_update((uint32_t *)fb, pitch);
-      osd_update((uint32_t *)(fb + SCREEN_HEIGHT * pitch), pitch);
       active = 0;
       RPI_SetGpioValue(LED1_PIN, active);
       update_palette();
@@ -259,7 +258,6 @@ void osd_set(int line, int attr, char *text) {
    }
    strncpy(buffer + line * LINELEN, text, len);
    osd_update((uint32_t *)fb, pitch);
-   osd_update((uint32_t *)(fb + SCREEN_HEIGHT * pitch), pitch);
 }