wic: add 'wic ls' command

Added empty 'wic ls' command that does nothing.
The functionality will be added by the next commits.

(From OE-Core rev: ba4613469cc2c3d3433be2e2f520f4fff6b3b333)

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

scripts/lib/wic/engine.py

@@ -225,6 +225,10 @@ def wic_list(args, scripts_path):
 
     return False
 
+def wic_ls(args, native_sysroot):
+    """List contents of partitioned image or vfat partition."""
+    pass
+
 def find_canned(scripts_path, file_name):
     """
     Find a file either by its path or by name in the canned files dir.