drivers/elog: Remove ELOG_PRERAM config

This change is being done for the following reasons:
1.  The CONFIG_ELOG_PRERAM is unused.
2.  We need to pull in elog.c into romstage because we are pulling the
    mrc_cache_stash_data function into romstage.
3.  Furquan says that we can rely on the linker to optimize out the
    unused 4KiB buffer in the early stages of boot, which allows us to
    get rid of the ELOG_PRERAM config.

BUG=b:117884485, b:150502246
BRANCH=None
TEST=./util/abuild/abuild -p none -t GOOGLE_NAMI -x -a -v

Change-Id: Id76cabc38e41e9bf79e1580a530c871a4ecef4ec
Signed-off-by: Shelley Chen <shchen@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45303
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/elog/Kconfig

@@ -23,12 +23,6 @@ config ELOG_CBMEM
 	 but it means that events added at runtime via the SMI handler
 	 will not be reflected in the CBMEM copy of the log.
 
-config ELOG_PRERAM
-	bool
-	default n
-	help
-	  This option will enable event logging from the preram stage.
-
 config ELOG_GSMI
 	depends on HAVE_SMI_HANDLER
 	bool "SMI interface to write and clear event log"

src/drivers/elog/Makefile.inc

@@ -1,7 +1,7 @@
-bootblock-$(CONFIG_ELOG_PRERAM) += elog.c
-verstage-$(CONFIG_ELOG_PRERAM) += elog.c
-romstage-$(CONFIG_ELOG_PRERAM) += elog.c
-postcar-$(CONFIG_ELOG_PRERAM) += elog.c
+bootblock-$(CONFIG_ELOG) += elog.c
+verstage-$(CONFIG_ELOG) += elog.c
+romstage-$(CONFIG_ELOG) += elog.c
+postcar-$(CONFIG_ELOG) += elog.c
 ramstage-$(CONFIG_ELOG) += elog.c
 
 smm-$(CONFIG_ELOG_GSMI) += elog.c gsmi.c