Make watchdogd enforcing.

Change-Id: I04969ca94d27535b3cdcfad55f092f98592b22f7
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>

watchdogd.te

 # watchdogd seclabel is specified in init.<board>.rc
 type watchdogd, domain;
-permissive watchdogd;
 allow watchdogd rootfs:file { entrypoint r_file_perms };
 allow watchdogd self:capability mknod;
 allow watchdogd device:dir { add_name write remove_name };