wic: add 'wic cp' command

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

[YOCTO #11283]

(From OE-Core rev: f0dcf39d52185430422cb0c94c7fe99c12764acd)

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

scripts/lib/wic/engine.py

@@ -309,6 +309,13 @@ def wic_ls(args, native_sysroot):
         path = args.path.path or '/'
         print(disk.dir(args.path.part, path))
 
+def wic_cp(args, native_sysroot):
+    """
+    Copy local file or directory to the vfat partition of
+    partitioned image.
+    """
+    pass
+
 def find_canned(scripts_path, file_name):
     """
     Find a file either by its path or by name in the canned files dir.