mb/siemens/mc_ehl: Remove subdir 'spd' from Makefile

Since commit 833bb448c5 ("mb/siemens/mc_ehl: Remove spd.bin from
CBFS"), the subdir 'spd' is no longer necessary.

Change-Id: Ibaf44e3181b2167aa83cffcc59835196e4cb5cdb
Signed-off-by: Mario Scheithauer <mario.scheithauer@siemens.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74780
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jan Samek <jan.samek@siemens.com>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>

src/mainboard/siemens/mc_ehl/Makefile.inc

@@ -1,7 +1,5 @@
 ## SPDX-License-Identifier: GPL-2.0-only
 
-subdirs-y += spd
-
 bootblock-y += bootblock.c
 
 romstage-y += romstage_fsp_params.c