nvme: fix CMB endianness confusion

The CMB is marked as DEVICE_LITTLE_ENDIAN, so the data must be
read/written as if it was little-endian output (in the case of
big endian, we get two swaps, one in the memory core and one
in nvme.c).
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Tested-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

hw/block/nvme.c

@@ -1177,16 +1177,13 @@ static void nvme_cmb_write(void *opaque, hwaddr addr, uint64_t data,
     unsigned size)
 {
     NvmeCtrl *n = (NvmeCtrl *)opaque;
-    memcpy(&n->cmbuf[addr], &data, size);
+    stn_le_p(&n->cmbuf[addr], size, data);
 }
 
 static uint64_t nvme_cmb_read(void *opaque, hwaddr addr, unsigned size)
 {
-    uint64_t val;
     NvmeCtrl *n = (NvmeCtrl *)opaque;
-
-    memcpy(&val, &n->cmbuf[addr], size);
-    return val;
+    return ldn_le_p(&n->cmbuf[addr], size);
 }
 
 static const MemoryRegionOps nvme_cmb_ops = {