Use CMD13 status directly for detection of SD card presence

The old readOCR() method is still used for ZuluSCSI v1.0 that
uses SPI access for the SD card.

src/ZuluSCSI.cpp

@@ -916,6 +916,16 @@ static void firmware_update()
   root.close();
 }
 
+// Checks if SD card is still present
+static bool poll_sd_card()
+{
+#ifdef SD_USE_SDIO
+  return SD.card()->status() != 0 && SD.card()->errorCode() == 0;
+#else
+  uint32_t ocr;
+  return SD.card()->readOCR(&ocr);
+#endif
+}
 
 // Place all the setup code that requires the SD card to be initialized here
 // Which is pretty much everything after platform_init and and platform_late_init
@@ -1123,10 +1133,9 @@ extern "C" void zuluscsi_main_loop(void)
         (uint32_t)(millis() - sd_card_check_time) > SDCARD_POLL_INTERVAL)
     {
       sd_card_check_time = millis();
-      uint32_t ocr;
-      if (!SD.card()->readOCR(&ocr))
+      if (!poll_sd_card())
       {
-        if (!SD.card()->readOCR(&ocr))
+        if (!poll_sd_card())
         {
           g_sdcard_present = false;
           logmsg("SD card removed, trying to reinit");