New Port: Eros Q Native

What works:
- LCD: 16-bit RGB565
- all buttons, including scrollwheel
- SD Card
- Battery level and charging/not charging status
- USB
- audio
- sample rate switching
- HP / LO detect, with "safe" fixed LO volume -
   LO volume will only be put to user-defined max volume
   if headphones are not present.
- rtc
- Plugins build, tried a couple and they seem OK
- Bootloader, installable to nand via usbboot

What doesn't work:
- Dual Boot
- power on/off has intermittent, low volume audio click
   (sometimes it's completely silent, sometimes there's
    a click)
- Audio uses 16-bit volume scaling, so clicking/popping
   is pretty bad at lower volumes - need 32 bit volume
   scaling, 24 bit I2S data
- USB HID keys not yet defined
- no jztool support

Unknowns:
- Stereo Switch pins: Direction select, AC_DC
   (probably not even hooked up)
- What is the actual purpose of the Stereo Swtich?
- How does the bluetooth module connect?

"Someday" stuff:
- get LCD working at higher bit depth
- Bluetooth

Change-Id: I70dda8fc092c6e3f4352f2245e4164193f803c33

firmware/drivers/audio/eros_qn_codec.c

@@ -0,0 +1,65 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2021 Andrew Ryabinin, Dana Conrad
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#include "system.h"
+#include "eros_qn_codec.h"
+#include "config.h"
+#include "audio.h"
+#include "audiohw.h"
+#include "settings.h"
+#include "pcm_sw_volume.h"
+
+static long int vol_l_hw = 0;
+static long int vol_r_hw = 0;
+
+void pcm5102_set_outputs(void)
+{
+    audiohw_set_volume(vol_l_hw, vol_r_hw);
+}
+
+/* this makes less sense here than it does in the audiohw-*.c file,
+ * but we need access to settings.h */
+void audiohw_set_volume(int vol_l, int vol_r)
+{
+    int l, r;
+
+    vol_l_hw = vol_l;
+    vol_r_hw = vol_r;
+
+    l = vol_l;
+    r = vol_r;
+
+#if (defined(HAVE_HEADPHONE_DETECTION) && defined(HAVE_LINEOUT_DETECTION))
+    /* make sure headphones aren't present - don't want to
+     * blow out our eardrums cranking it to full */
+    if (lineout_inserted() && !headphones_inserted())
+    {
+        l = r = global_settings.volume_limit * 10;
+    }
+    else
+    {
+        l = vol_l;
+        r = vol_r;
+    }
+#endif
+
+    pcm_set_master_volume(l, r);
+}