lsm: remove redundant NULL check in security_init()

Since commit 5137e583ba26 ("lsm: cleanup the debug and console output
in lsm_init.c"), the NULL check for lsm_order_legacy in security_init()
has no effect.

So remove the check.

No functional change.

Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>