Revert "SELinux: Enable setting security contexts on rootfs inodes."

This reverts commit 78d36d21.

Drop this duplicate patch. This patch is already upstreamed in v4.4. Commits
5c73fceb (SELinux: Enable setting security contexts on rootfs inodes.),
12f348b9 (SELinux: rename SE_SBLABELSUPP to SBLABEL_MNT), and
b43e725d (SELinux: use a helper function to determine seclabel),
for reference.

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>