src/device/dram/Makefile.inc: specify one file per line

A trivial follow-up on CB:67060.  This makes contents of the file look a
bit less regular, but more like the rest Makefile.inc in the code base.

Change-Id: I772d37825e4b59cf927637dc39bfb3ee06115860
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/77533
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/device/dram/Makefile.inc b/src/device/dram/Makefile.inc
index 64f1dba..7772db2 100644
--- a/src/device/dram/Makefile.inc
+++ b/src/device/dram/Makefile.inc
@@ -1,7 +1,8 @@
 ## SPDX-License-Identifier: GPL-2.0-only
 
 romstage-y += ddr_common.c
-ramstage-y += ddr_common.c spd.c
+ramstage-y += ddr_common.c
+ramstage-y += spd.c
 
 romstage-$(CONFIG_USE_DDR5) += ddr5.c
 ramstage-$(CONFIG_USE_DDR5) += ddr5.c
@@ -9,7 +10,8 @@
 romstage-$(CONFIG_USE_LPDDR4) += lpddr4.c
 ramstage-$(CONFIG_USE_LPDDR4) += lpddr4.c
 
-romstage-$(CONFIG_USE_DDR4) += ddr4.c rcd.c
+romstage-$(CONFIG_USE_DDR4) += ddr4.c
+romstage-$(CONFIG_USE_DDR4) += rcd.c
 ramstage-$(CONFIG_USE_DDR4) += ddr4.c
 
 romstage-$(CONFIG_USE_DDR3) += ddr3.c