baytrail: initialize common SSC functionality

The SSC (storage control cluster) houses the SD, SDIO, and eMMC
interfaces. The scc cofniguration function, baytrail_init_scc(),
is ran in the pre device stage to initialize the SCC. The eMMC
is expected to be configured for version 4.5.

BUG=chrome-os-partner:23966
BRANCH=None
TEST=Built and booted with some other eMMC changes into login screen off
     of eMMC device.

Change-Id: I81cc755a790b7e43ad234a8201dae480277202c8
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/176535
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/4966
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/soc/intel/baytrail/Makefile.inc

@@ -39,6 +39,7 @@ ramstage-$(CONFIG_HAVE_REFCODE_BLOB) += refcode.c
 ramstage-y += sata.c
 ramstage-y += acpi.c
 ramstage-y += lpe.c
+ramstage-y += scc.c
 
 # Remove as ramstage gets fleshed out
 ramstage-y += placeholders.c