hw/sd/sdhci: Do not force sdhci_mmio_*_ops onto all SD controllers

Since commit c0a55a0c9da2 "hw/sd/sdhci: Support big endian SD host controller
interfaces" sdhci_common_realize() forces all SD card controllers to use either
sdhci_mmio_le_ops or sdhci_mmio_be_ops, depending on the "endianness" property.
However, there are device models which use different MMIO ops: TYPE_IMX_USDHC
uses usdhc_mmio_ops and TYPE_S3C_SDHCI uses sdhci_s3c_mmio_ops.

Forcing sdhci_mmio_le_ops breaks SD card handling on the "sabrelite" board, for
example. Fix this by defaulting the io_ops to little endian and switch to big
endian in sdhci_common_realize() only if there is a matchig big endian variant
available.

Fixes: c0a55a0c9da2 ("hw/sd/sdhci: Support big endian SD host controller
interfaces")

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Message-Id: <20230709080950.92489-1-shentey@gmail.com>

hw/sd/sdhci.c

@@ -1382,6 +1382,8 @@ void sdhci_initfn(SDHCIState *s)
 
     s->insert_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, sdhci_raise_insertion_irq, s);
     s->transfer_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, sdhci_data_transfer, s);
+
+    s->io_ops = &sdhci_mmio_le_ops;
 }
 
 void sdhci_uninitfn(SDHCIState *s)
@@ -1399,9 +1401,13 @@ void sdhci_common_realize(SDHCIState *s, Error **errp)
 
     switch (s->endianness) {
     case DEVICE_LITTLE_ENDIAN:
-        s->io_ops = &sdhci_mmio_le_ops;
+        /* s->io_ops is little endian by default */
         break;
     case DEVICE_BIG_ENDIAN:
+        if (s->io_ops != &sdhci_mmio_le_ops) {
+            error_setg(errp, "SD controller doesn't support big endianness");
+            return;
+        }
         s->io_ops = &sdhci_mmio_be_ops;
         break;
     default: