lsm: CONFIG_LSM can depend on CONFIG_SECURITY

When CONFIG_SECURITY is not set, CONFIG_LSM (builtin_lsm_order) does
not need to be visible and settable since builtin_lsm_order is defined in
security.o, which is only built when CONFIG_SECURITY=y.

So make CONFIG_LSM depend on CONFIG_SECURITY.

Fixes: 13e735c0 ("LSM: Introduce CONFIG_LSM")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
[PM: subj tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>