baytrail: log reset, power, and wake events in elog

When CONFIG_ELOG is selected the reset, power, and wake
events are logged in the eventlog.

BUG=chrome-os-partner:24907
BRANCH=rambi,squawks
TEST=Various resets and wake sources. Interrogated eventlog
     to ensure results are expected.

Change-Id: Ia68548562917be6c2a0d8d405a5b519102b8c563
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/181983
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/5033
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/soc/intel/baytrail/Makefile.inc

@@ -47,6 +47,7 @@ ramstage-y += sd.c
 ramstage-y += perf_power.c
 ramstage-y += stage_cache.c
 romstage-y += stage_cache.c
+ramstage-$(CONFIG_ELOG) += elog.c
 
 # Remove as ramstage gets fleshed out
 ramstage-y += placeholders.c