wic: add system_id attribute to Partition

Added Partition.system_id attribute and initialized it
from parse result of wks option --system-id. It will be
used by the wic code below the call stack to set partition
system id.

[YOCTO #9096]

(From OE-Core rev: 4f195a5b7574ebff8fbdb3045daa71f173f97a30)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/partition.py

@@ -57,6 +57,7 @@ class Partition(object):
         self.size = args.size
         self.source = args.source
         self.sourceparams = args.sourceparams
+        self.system_id = args.system_id
         self.use_uuid = args.use_uuid
         self.uuid = args.uuid
         if args.use_uuid and not self.uuid: