hw/ssi/imx_spi.c: Remove MSGDATA register support

From the documentation it is not clear what this SPI register is about.

Moreover, neither linux driver nor xvisor driver are using this SPI register.

For now we just remove it and issue a log on register write access.
Signed-off-by: NJean-Christophe Dubois <jcd@tribudubois.net>
Message-id: 20170107122047.26300-1-jcd@tribudubois.net
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/ssi/imx_spi.c

@@ -320,9 +320,6 @@ static void imx_spi_write(void *opaque, hwaddr offset, uint64_t value,
                       TYPE_IMX_SPI, __func__);
         break;
     case ECSPI_TXDATA:
-    case ECSPI_MSGDATA:
-        /* Is there any difference between TXDATA and MSGDATA ? */
-        /* I'll have to look in the linux driver */
         if (!imx_spi_is_enabled(s)) {
             /* Ignore writes if device is disabled */
             break;
@@ -380,6 +377,14 @@ static void imx_spi_write(void *opaque, hwaddr offset, uint64_t value,
         }
 
         break;
+    case ECSPI_MSGDATA:
+        /* it is not clear from the spec what MSGDATA is for */
+        /* Anyway it is not used by Linux driver */
+        /* So for now we just ignore it */
+        qemu_log_mask(LOG_UNIMP,
+                      "[%s]%s: Trying to write to MSGDATA, ignoring\n",
+                      TYPE_IMX_SPI, __func__);
+        break;
     default:
         s->regs[index] = value;