selinux: simple cleanup for cond_read_node()

The node->cur_state and len can be read in a single call of next_entry().
And setting len before reading is a dead write so can be eliminated.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
(Minor tweak to the length parameter in the call to next_entry())
Signed-off-by: Paul Moore <pmoore@redhat.com>