soc/intel/tgl: move DIMM_SPD_SIZE from mb to SoC Kconfig

All TGL mainboards are setting DIMM_SPD_SIZE to 512. Thus, default to
512 in the SoC Kconfig and drop it from the mainboard Kconfigs.

Change-Id: I9fd947b61c984e10bd5fba20b73280b08623a008
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62766
Reviewed-by: Felix Singer <felixsinger@posteo.net>
Reviewed-by: Tim Crawford <tcrawford@system76.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/soc/intel/tigerlake/Kconfig b/src/soc/intel/tigerlake/Kconfig
index 6d20112..2b673cab 100644
--- a/src/soc/intel/tigerlake/Kconfig
+++ b/src/soc/intel/tigerlake/Kconfig
@@ -94,6 +94,9 @@
 	default 16 if SOC_INTEL_TIGERLAKE_PCH_H
 	default 8
 
+config DIMM_SPD_SIZE
+	default 512
+
 config DCACHE_RAM_BASE
 	default 0xfef00000