mosys: display full memory part number

The length of memory part number has been lengthened in CL:426759

BUG=b:35583545
BRANCH=none
TEST=emerge-veyron_mickey mosys;
     ./mosys memory spd print all

Change-Id: I4423f44003ea77f91a4045146541303d48b3fb49
Signed-off-by: jiazi Yang <Tomato_Yang@asus.com>
Reviewed-on: https://chromium-review.googlesource.com/468650
Commit-Ready: Tomato Yang <tomato_yang@asus.corp-partner.google.com>
Tested-by: Tomato Yang <tomato_yang@asus.corp-partner.google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/spd/nonspd.c b/lib/spd/nonspd.c
index 4cbfca0..66944d8 100644
--- a/lib/spd/nonspd.c
+++ b/lib/spd/nonspd.c
@@ -176,10 +176,10 @@
 
 	case SPD_GET_PART_NUMBER:
 	{
-		char part[19];
+		char part[sizeof(info->part_num)+1];
 
-		memcpy(part, &info->part_num[0], 18);
-		part[18] = '\0';
+		memcpy(part, &info->part_num[0], sizeof(info->part_num));
+		part[sizeof(info->part_num)] = '\0';
 		kv_pair_fmt(kv, "part_number", "%s", part);
 
 		ret = 1;