Allow imxtract to extract part of script image.

Scripts are multi-file images, the imxtract command should handle them
in the same manner.

Signed-off-by: Pierre Aubert <p.aubert@staubli.com>
diff --git a/common/cmd_ximg.c b/common/cmd_ximg.c
index 8b8645c..d033c15 100644
--- a/common/cmd_ximg.c
+++ b/common/cmd_ximg.c
@@ -88,7 +88,8 @@
 		image_print_contents(hdr);
 #endif
 
-		if (!image_check_type(hdr, IH_TYPE_MULTI)) {
+		if (!image_check_type(hdr, IH_TYPE_MULTI) &&
+		    !image_check_type(hdr, IH_TYPE_SCRIPT)) {
 			printf("Wrong Image Type for %s command\n",
 					cmdtp->name);
 			return 1;