mb/ocp/tiogapass: Implement mainboard_dimm_slot_exists

The board has 24 slots for DDR4 ECC RDIMMs and it has 2 CPU sockets,
where each is connected to 12 DIMMs. Every socket supports up to
6 channels, thus every channel is connected to 2 DIMMs.

Implement mainboard_dimm_slot_exists accordingly to advertise all slots
as SMBIOS type 17.

TEST: Found all installed DIMMs advertised through SMBIOS on
      ocp/tiogapass.

Change-Id: I31cb4a89aa11258ac04eb69a0e9c86f258280484
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/85318
Reviewed-by: Christian Walter <christian.walter@9elements.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/ocp/tiogapass/romstage.c

@@ -1,13 +1,14 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
-#include <fsp/api.h>
-#include <FspmUpd.h>
 #include <drivers/ipmi/ipmi_if.h>
 #include <drivers/ipmi/ocp/ipmi_ocp.h>
+#include <fsp/api.h>
+#include <FspmUpd.h>
+#include <gpio.h>
+#include <soc/ddr.h>
+#include <soc/gpio_soc_defs.h>
 #include <soc/romstage.h>
 #include <string.h>
-#include <gpio.h>
-#include <soc/gpio_soc_defs.h>
 #include <skxsp_tp_iio.h>
 
 #include "ipmi.h"
@@ -64,3 +65,15 @@ void mainboard_memory_init_params(FSPM_UPD *mupd)
 	mupd->FspmConfig.GpioConfig.GpioTable = NULL;
 	mupd->FspmConfig.GpioConfig.NumberOfEntries = 0;
 }
+
+bool mainboard_dimm_slot_exists(uint8_t socket, uint8_t channel, uint8_t dimm)
+{
+	if (socket >= CONFIG_MAX_SOCKET)
+		return false;
+	if (channel >= 6)
+		return false;
+	if (dimm >= 2)
+		return false;
+
+	return true;
+}