gpt: add optional parameter type in gpt command

code under flag CONFIG_PARTITION_TYPE_GUID
add parameter "type" to select partition type guid

example of use with gpt command :

  partitions = uuid_disk=${uuid_gpt_disk}; \
      name=boot,size=0x6bc00,uuid=${uuid_gpt_boot}; \
      name=root,size=0x7538ba00,uuid=${uuid_gpt_root}, \
         type=0fc63daf-8483-4772-8e79-3d69d8477de4;

  gpt write mmc 0 $partitions

Signed-off-by: Patrick Delaunay <patrick.delaunay73@gmail.com>
diff --git a/include/part.h b/include/part.h
index 8ea9b30..8b5ac12 100644
--- a/include/part.h
+++ b/include/part.h
@@ -93,6 +93,9 @@
 #ifdef CONFIG_PARTITION_UUIDS
 	char	uuid[37];	/* filesystem UUID as string, if exists	*/
 #endif
+#ifdef CONFIG_PARTITION_TYPE_GUID
+	char	type_guid[37];	/* type GUID as string, if exists	*/
+#endif
 } disk_partition_t;
 
 /* Misc _get_dev functions */