net: ehea: Mark expected switch fall-through

Mark switch cases where we are expecting to fall through.

This patch fixes the following warning:

drivers/net/ethernet/ibm/ehea/ehea_main.c: In function 'ehea_mem_notifier':
include/linux/printk.h:311:2: warning: this statement may fall through [-Wimplicit-fallthrough=]
  printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/ibm/ehea/ehea_main.c:3253:3: note: in expansion of macro 'pr_info'
   pr_info("memory offlining canceled");
   ^~~~~~~
drivers/net/ethernet/ibm/ehea/ehea_main.c:3256:2: note: here
  case MEM_ONLINE:
  ^~~~

Notice that, in this particular case, the code comment is
modified in accordance with what GCC is expecting to find.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/ehea/ehea_main.c

@@ -3251,7 +3251,7 @@ static int ehea_mem_notifier(struct notifier_block *nb,
 	switch (action) {
 	case MEM_CANCEL_OFFLINE:
 		pr_info("memory offlining canceled");
-		/* Fall through: re-add canceled memory block */
+		/* Fall through - re-add canceled memory block */
 
 	case MEM_ONLINE:
 		pr_info("memory is going online");