use proper fallthrough annotations

In some cases in the generic code, we were already using switch/case
fallthrough annotations comments, though in a way which might not be
understood by most compilers.

Replace two non-standard /* no break */ comments with our fallthrough;
statement-like macro, to make this visible to the compiler.
Also use this macro in place of an /* Fall through */ comment, to be
more consistent.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

common/command.c

@@ -484,7 +484,7 @@ int cmd_get_data_size(const char *arg, int default_size)
 		case 'q':
 			if (MEM_SUPPORT_64BIT_DATA)
 				return 8;
-			/* no break */
+			fallthrough;
 		default:
 			return CMD_DATA_SIZE_ERR;
 		}

lib/tiny-printf.c

@@ -282,7 +282,7 @@ static int _vprintf(struct printf_info *info, const char *fmt, va_list va)
 					break;
 				}
 				islong = true;
-				/* no break */
+				fallthrough;
 			case 'x':
 				if (islong) {
 					num = va_arg(va, unsigned long);

net/net.c

@@ -1559,7 +1559,7 @@ common:
 			puts("*** ERROR: `ipaddr' not set\n");
 			return 1;
 		}
-		/* Fall through */
+		fallthrough;
 
 #ifdef CONFIG_CMD_RARP
 	case RARP: