[PATCH 3/6] hw/net/imx_fec: Rewrite fall through comments

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

GCC9 is confused by this comment when building with CFLAG
-Wimplicit-fallthrough=2:

  hw/net/imx_fec.c: In function ‘imx_eth_write’:
  hw/net/imx_fec.c:906:12: error: this statement may fall through [-Werror=implicit-fallthrough=]
    906 |         if (unlikely(single_tx_ring)) {
        |            ^
  hw/net/imx_fec.c:912:5: note: here
    912 |     case ENET_TDAR:     /* FALLTHROUGH */
        |     ^~~~
  cc1: all warnings being treated as errors

Rewrite the comments in the correct place,  using 'fall through'
which is recognized by GCC and static analyzers.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
Cc: Peter Chubb <peter.chubb@nicta.com.au>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Jason Wang <jasowang@redhat.com>
Cc: qemu-arm@nongnu.org
---
 hw/net/imx_fec.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/hw/net/imx_fec.c b/hw/net/imx_fec.c
index bd99236864..30cc07753d 100644
--- a/hw/net/imx_fec.c
+++ b/hw/net/imx_fec.c
@@ -901,15 +901,17 @@ static void imx_eth_write(void *opaque, hwaddr offset, uint64_t value,
             s->regs[index] = 0;
         }
         break;
-    case ENET_TDAR1:    /* FALLTHROUGH */
-    case ENET_TDAR2:    /* FALLTHROUGH */
+        /* fall through */
+    case ENET_TDAR1:
+    case ENET_TDAR2:
         if (unlikely(single_tx_ring)) {
             qemu_log_mask(LOG_GUEST_ERROR,
                           "[%s]%s: trying to access TDAR2 or TDAR1\n",
                           TYPE_IMX_FEC, __func__);
             return;
         }
-    case ENET_TDAR:     /* FALLTHROUGH */
+        /* fall through */
+    case ENET_TDAR:
         if (s->regs[ENET_ECR] & ENET_ECR_ETHEREN) {
             s->regs[index] = ENET_TDAR_TDAR;
             imx_eth_do_tx(s, index);
-- 
2.21.0