ipa-firmware: Write the firmware parts to a file

The first non working version to dump the content of the sdp
to the terminal..
diff --git a/openbsc/include/openbsc/ipaccess.h b/openbsc/include/openbsc/ipaccess.h
index f34cfbd..86248aa 100644
--- a/openbsc/include/openbsc/ipaccess.h
+++ b/openbsc/include/openbsc/ipaccess.h
@@ -89,6 +89,7 @@
 struct sdp_header_item {
 	struct sdp_header_entry header_entry;
 	struct llist_head entry;
+	off_t absolute_offset;
 };
 
 struct sdp_header {