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/classes/kernel.bbclass

@@ -613,8 +613,6 @@ kernel_do_deploy() {
 		ln -sf ${base_name}.bin ${DEPLOYDIR}/${type}
 	done
 
-	cp ${COREBASE}/meta/files/deploydir_readme.txt ${DEPLOYDIR}/README_-_DO_NOT_DELETE_FILES_IN_THIS_DIRECTORY.txt
-
 	cd ${B}
 	# Update deploy directory
 	for type in ${KERNEL_IMAGETYPES} ; do