[Timers] Do not enable serial console by default; this change should not

be propagated to master.

src/config.h

  */
 
 #define	CONSOLE_FIRMWARE	/* Default BIOS console */
-#define	CONSOLE_SERIAL		/* Serial port */
+#undef	CONSOLE_SERIAL		/* Serial port */
 #undef	CONSOLE_DIRECT_VGA	/* Direct access to VGA card */
 #undef	CONSOLE_BTEXT		/* Who knows what this does? */
 #undef	CONSOLE_PC_KBD		/* Direct access to PC keyboard */