dumpheader: Add default serial number in the header

Whenever the serialNo is empty, use a default serial
number (all zeroes) so that scripts/apps that decode
the dump header would not throw errors.

Verified that the default serial number is utilized.

Change-Id: I0d9a8cc9e257ed0a852aaca5e6cb0c1833abd41e
Signed-off-by: Gopichand Paturi <[email protected]>

Author: gopichand-paturi

dump/tools/common/include/gendumpheader

@@ -555,6 +555,10 @@ function plat_dump_header() {
 
 #main function
 function gen_header_package() {
+    if [ -z "$serialNo" ]; then
+        serialNo="0000000"
+    fi
+
     dump_file_entry
     dump_section_entry
     if [ "$dump_type" = "$OP_DUMP" ]; then