Label at end of compound statements is a C2x extension, so add an empty instruction.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reported-by: kernel test robot <lkp@intel.com>
Fixes: 807977260ae4 ("speakup: Add /dev/synthu device")
Closes: https://lore.kernel.org/oe-kbuild-all/202403090122.cpUNsozM-lkp@intel.com/

Index: linux-6.4/drivers/accessibility/speakup/devsynth.c
===================================================================
--- linux-6.4.orig/drivers/accessibility/speakup/devsynth.c
+++ linux-6.4/drivers/accessibility/speakup/devsynth.c
@@ -108,6 +108,7 @@ static ssize_t speakup_file_writeu(struc
 				break;
 			}
 drop:
+			;
 		}
 
 		count -= bytes;