Doc/mainboard_io_trap_handler_sample.c: Drop file

Looks like nothing references this example. Remove it. If one needs an
example, there's several mainboards which contain an I/O trap handler.

Change-Id: I4a238fbf354926cb6568e1709bfb79cc546dfd73
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58322
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>

Documentation/mainboard_io_trap_handler_sample.c

@@ -1,37 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-
-#include <arch/io.h>
-#include <console/console.h>
-#include <cpu/x86/smm.h>
-#include <soc/pm.h>
-#include <soc/smm.h>
-#include <elog.h>
-#include <ec/google/chromeec/ec.h>
-#include <soc/gpio.h>
-#include <soc/iomap.h>
-#include <soc/nvs.h>
-#include <soc/pm.h>
-#include <soc/smm.h>
-#include "ec.h"
-#include "gpio.h"
-
-int mainboard_io_trap_handler(int smif)
-{
-       switch (smif) {
-       case 0x99:
-               printk(BIOS_DEBUG, "Sample\n");
-               gnvs->smif = 0;
-               break;
-       default:
-               return 0;
-       }
-
-       /* On success, the IO Trap Handler returns 0
-        * On failure, the IO Trap Handler returns a value != 0
-        *
-        * For now, we force the return value to 0 and log all traps to
-        * see what's going on.
-        */
-       //gnvs->smif = 0;
-       return 1;
-}