mb/siemens/mc_ehl: Move SPD data to variant directory

Since the variants can have different memory move the SPD related
content to the variant directory.

Change-Id: I38aa5e7514437bfcc61c38d64f0ba6f19350810d
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56036
Reviewed-by: Mario Scheithauer <mario.scheithauer@siemens.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/siemens/mc_ehl/spd/Makefile.inc

@@ -1,3 +0,0 @@
-## SPDX-License-Identifier: GPL-2.0-only
-
-SPD_SOURCES = mc_ehl	# 0b000

src/mainboard/siemens/mc_ehl/variants/mc_ehl1/Makefile.inc

@@ -3,3 +3,7 @@
 bootblock-y += gpio.c
 romstage-y += memory.c
 ramstage-y += gpio.c
+
+SPD_SOURCES = mc_ehl1	# 0b000
+LIB_SPD_DEPS := $(foreach f, $(SPD_SOURCES), \
+			src/mainboard/$(MAINBOARDDIR)/variants/$(VARIANT_DIR)/spd/$(f).spd.hex)