mosys: Increase part number string size.

BUG=b:119535940
TEST=Manually test on DUT.
     Check that mosys output matches vendor part number.

Change-Id: I7fa6c2eaacf1b7deb57f06465ca94fc3068cabd2
Reviewed-on: https://chromium-review.googlesource.com/c/1337350
Tested-by: Cheng-Han Yang <chenghan@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Commit-Queue: Cheng-Han Yang <chenghan@chromium.org>
(cherry picked from commit 002ad2f5add7e750f2fa303af59fbf0afd79706b)
Reviewed-on: https://chromium-review.googlesource.com/1360099
Commit-Ready: David Wu <david_wu@quanta.corp-partner.google.com>
Tested-by: David Wu <david_wu@quanta.corp-partner.google.com>
Reviewed-by: Cheng-Han Yang <chenghan@chromium.org>
Reviewed-by: Peter Hung <peter.hung@quanta.corp-partner.google.com>
diff --git a/lib/spd/ddr4.c b/lib/spd/ddr4.c
index e9279bd..fd87e4a 100644
--- a/lib/spd/ddr4.c
+++ b/lib/spd/ddr4.c
@@ -158,10 +158,10 @@
 
 	case SPD_GET_PART_NUMBER:
 	{
-		char part[19];
+		char part[20];
 
-		memcpy(part, &byte[DDR4_SPD_REG_MODULE_PART_NUM_0], 18);
-		part[18] = '\0';
+		memcpy(part, &byte[DDR4_SPD_REG_MODULE_PART_NUM_0], 19);
+		part[19] = '\0';
 		kv_pair_fmt(kv, "part_number", "%s", part);
 
 		ret = 1;