Change return value on error.

On wrong parameters a error is signalized to the calling function.

Change-Id: I484443fdb39938e20382edc9246d5ec546a5c960
Signed-off-by: Mathias K <kesmtp@freenet.de>
Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>
Reviewed-on: http://openocd.zylin.com/282
Tested-by: jenkins
Reviewed-by: Øyvind Harboe <oyvindharboe@gmail.com>

src/target/armv4_5.c

@@ -784,10 +784,8 @@ COMMAND_HANDLER(handle_arm_disassemble_command)
 		break;
 	default:
 usage:
-		command_print(CMD_CTX,
-			"usage: arm disassemble <address> [<count> ['thumb']]");
 		count = 0;
-		retval = ERROR_FAIL;
+		retval = ERROR_COMMAND_SYNTAX_ERROR;
 	}
 
 	while (count-- > 0) {