scsi: fas216: Use fallthrough pseudo-keyword

Replace /*FALLTHROUGH*/ comment with pseudo-keyword macro 'fallthrough'.

Link: https://lore.kernel.org/r/20210518131823.2586-1-jj251510319013@gmail.comSigned-off-by: Wei Ming Chen <jj251510319013@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/arm/fas216.c

@@ -1479,7 +1479,7 @@ static void fas216_busservice_intr(FAS216_Info *info, unsigned int stat, unsigne
 
 		if (msgqueue_msglength(&info->scsi.msgs) > 1)
 			fas216_cmd(info, CMD_SETATN);
-		/*FALLTHROUGH*/
+		fallthrough;
 
 	/*
 	 * Any          -> Message Out