crossystem: Add the ddr_type field on crossystem for querying DDR RAM type

Samsung want to know what memory type on the device. So this CL adds a
new field ddr_type to crossystem utility in order to query this info.

It is only available on ARM platform so far.

BUG=chrome-os-partner:10857
TEST=Built and boot on Snow successfuly. On userspace, query the field via:
localhost ~ # crossystem ddr_type
ddr3

Change-Id: I01d1dec412fe4052e1ea6cfe2e53830da97a710b
Signed-off-by: Tom Wai-Hong Tam <waihong@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/26411
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/utility/crossystem_main.c b/utility/crossystem_main.c
index e7320c9..ecd1e4f 100644
--- a/utility/crossystem_main.c
+++ b/utility/crossystem_main.c
@@ -37,6 +37,7 @@
   {"arch", IS_STRING, "Platform architecture"},
   {"cros_debug", 0, "OS should allow debug features"},
   {"dbg_reset", CAN_WRITE, "Debug reset mode request (writable)"},
+  {"ddr_type", IS_STRING, "Type of DDR RAM"},
   {"disable_dev_request", CAN_WRITE, "Disable virtual dev-mode on next boot"},
   {"dev_boot_usb", CAN_WRITE,
    "Enable developer mode boot from USB/SD (writable)"},