kernel, license, sstate, rootfs.py: Remove deploy directory README

It isn't clear that the README_-_DO_NOT_DELETE_FILES_IN_THIS_DIRECTORY.txt
file in the deploy directory warrants the complexity it brings elsewhere.
Let's just remove it entirely.

In particular, if two do_image_complete tasks run in parallel they risk
both trying to put their image into ${DEPLOY_DIR_IMAGE} at the same time.
Both will contain a README_-_DO_NOT_DELETE_FILES_IN_THIS_DIRECTORY.txt
file. In theory this should be safe because "cp -alf" will just cause one
to overwrite the other. Unfortunately, coreutils cp also has a race[1]
which means that if one copy creates the file at just the wrong point the
other will fail with:

 cp: cannot create hard link ‘..../tmp-glibc/deploy/images/pantera/README_-_DO_NOT_DELETE_FILES_IN_THIS_D.txt’ to
+‘..../tmp-glibc/work/rage_against-oe-linux-gnueabi/my-own-image/1.0-r0/deploy-my-own-image-complete/README_-_DO_NOT_DELETE_FILES_IN_THIS_DIRECTORY.txt’: File exists

[1] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25680

(From OE-Core rev: 71e9e88847d7000781642ea6187ebd8f40dfdcfe)

Signed-off-by: Mike Crowe <mac@mcrowe.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oe/rootfs.py

@@ -189,10 +189,6 @@ class Rootfs(object, metaclass=ABCMeta):
 
         shutil.copytree(postinst_intercepts_dir, intercepts_dir)
 
-        shutil.copy(self.d.expand("${COREBASE}/meta/files/deploydir_readme.txt"),
-                    self.deploydir +
-                    "/README_-_DO_NOT_DELETE_FILES_IN_THIS_DIRECTORY.txt")
-
         execute_pre_post_process(self.d, pre_process_cmds)
 
         if self.progress_reporter: