lsm: rename the lsm order variables for consistency

lsm: rename the lsm order variables for consistency

Rename the builtin_lsm_order variable to lsm_order_builtin,
chosen_lsm_order to lsm_order_cmdline, chosen_major_lsm to
lsm_order_legacy, ordered_lsms[] to lsm_order[], and exclusive
to lsm_exclusive.

This patch also renames the associated kernel command line parsing
functions and adds some basic function comment blocks.  The parsing
function choose_major_lsm() was renamed to lsm_choose_security(),
choose_lsm_order() to lsm_choose_lsm(), and enable_debug() to
lsm_debug_enable().

Reviewed-by: Kees Cook <kees@kernel.org>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>