selinux: Remove SECURITY_SELINUX_BOOTPARAM_VALUE

In preparation for removing CONFIG_DEFAULT_SECURITY, this removes the
soon-to-be redundant SECURITY_SELINUX_BOOTPARAM_VALUE. Since explicit
ordering via CONFIG_LSM or "lsm=" will define whether an LSM is enabled or
not, this CONFIG will become effectively ignored, so remove it. However,
in order to stay backward-compatible with "security=selinux", the enable
variable defaults to true.

Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 49865f1..c5d9fbbb 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -121,9 +121,8 @@ __setup("enforcing=", enforcing_setup);
 #define selinux_enforcing_boot 1
 #endif
 
+int selinux_enabled __lsm_ro_after_init = 1;
 #ifdef CONFIG_SECURITY_SELINUX_BOOTPARAM
-int selinux_enabled = CONFIG_SECURITY_SELINUX_BOOTPARAM_VALUE;
-
 static int __init selinux_enabled_setup(char *str)
 {
 	unsigned long enabled;
@@ -132,8 +131,6 @@ static int __init selinux_enabled_setup(char *str)
 	return 1;
 }
 __setup("selinux=", selinux_enabled_setup);
-#else
-int selinux_enabled = 1;
 #endif
 
 static unsigned int selinux_checkreqprot_boot =