menu_cbs_ok: re-adjust audio rates when the resolution dropdown changes refresh

Picking an entry from Settings -> Video -> Output -> Screen Resolution
runs action_cb_push_dropdown_item_resolution, which applied the new
refresh rate by calling video_monitor_set_refresh_rate() directly.

That function only writes settings->floats.video_refresh_rate and
pushes an OSD message.  The rest of the work lives in the
RARCH_DRIVER_CTL_SET_REFRESH_RATE case in retroarch.c, which also
resets audio_st->src_ratio_orig / src_ratio_curr, calls
driver_adjust_system_rates() so audio_st->input tracks the new
display rate, and recomputes the DRC threshold via
audio_driver_update_drc_threshold().

Because the dropdown skipped all of that, the resampler kept
converting for the old refresh rate after a mode change.  Menu
background music (Menu Sounds -> Enable BGM Sound) is fed through
audio_driver_menu_sample() -> audio_driver_flush(), which resamples
with the stale src_ratio_curr, so it becomes garbled the moment the
mode is switched and stays that way until something else re-adjusts
the rates.  It is loudest on a 120 Hz -> 60 Hz switch, where the
ratio is off by 2x, but the defect is not display- or
platform-specific: any refresh change made through this dropdown hits
it.

Route the change through driver_ctl() instead.  This is how every
refresh-rate case in menu_setting.c (VIDEO_REFRESH_RATE,
VIDEO_REFRESH_RATE_AUTO, VIDEO_REFRESH_RATE_POLLED) already applies a
change, so the dropdown was the odd one out.

driver.h is already included here, so no new dependency.  The
early-out in video_monitor_set_refresh_rate() for an unchanged value
still applies; only the audio re-adjustment is added, and it is
harmless when the rate did not actually move.

menu/cbs/menu_cbs_ok.c

@@ -7514,7 +7514,18 @@ int action_cb_push_dropdown_item_resolution(const char *path,
       if (refreshrate == (60.0f * refresh_mod) - 1)
          refresh_exact = 59.94f * refresh_mod;
 
-      video_monitor_set_refresh_rate(refresh_exact);
+      /* Apply through driver_ctl rather than calling
+       * video_monitor_set_refresh_rate() directly.  Updating the
+       * config float is only half the job: the driver_ctl case also
+       * resets the resampler ratio, re-runs
+       * driver_adjust_system_rates() and recomputes the DRC
+       * threshold.  Skipping those leaves the audio resampler
+       * converting for the previous refresh rate until something
+       * else happens to re-adjust the rates - on a 120 Hz -> 60 Hz
+       * switch the ratio is wrong by 2x and the output is audibly
+       * garbled.  Every refresh-rate case in menu_setting.c already
+       * applies changes this way. */
+      driver_ctl(RARCH_DRIVER_CTL_SET_REFRESH_RATE, &refresh_exact);
 
       settings->uints.video_fullscreen_x = width;
       settings->uints.video_fullscreen_y = height;