Revert "security,lockdown,selinux: implement SELinux lockdown"

This reverts commit 59438b4647.

This unblocks the booting of Android on newer kernels. It is a temporary
workaround and the correct fix is to add new core sepolicy.

Bug: 148822198
Change-Id: Ic521cb760c867c12dfcb7d2752280fbb0eddb82c
Signed-off-by: Alistair Delva <adelva@google.com>

include/linux/security.h

@@ -128,8 +128,6 @@ enum lockdown_reason {
 	LOCKDOWN_CONFIDENTIALITY_MAX,
 };
 
-extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];
-
 /* These functions are in security/commoncap.c */
 extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
 		       int cap, unsigned int opts);