security: Add LSMs dependencies to CONFIG_LSM

Thanks to the previous commit, this gives the opportunity to users, when
running make oldconfig, to update the list of enabled LSMs at boot time
if an LSM has just been enabled or disabled in the build.  Moreover,
this list only makes sense if at least one LSM is enabled.

Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: James Morris <jmorris@namei.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Link: https://lore.kernel.org/r/20210215122513.1773897-4-mic@digikod.net

security/Kconfig

@@ -277,6 +277,10 @@ endchoice
 
 config LSM
 	string "Ordered list of enabled LSMs"
+	depends on SECURITY_LOCKDOWN_LSM || SECURITY_YAMA || SECURITY_LOADPIN || \
+		SECURITY_SAFESETID || INTEGRITY || SECURITY_SELINUX || \
+		SECURITY_SMACK || SECURITY_TOMOYO || SECURITY_APPARMOR || \
+		BPF_LSM
 	default "lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK
 	default "lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR
 	default "lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO