Minimize public policy

Ideally, public should only contain APIs (types / attributes) for
vendor. The other statements like allow/neverallow/typeattributes are
regarded as implementation detail for platform and should be in private.

Bug: 232023812
Test: m selinux_policy
Test: diff <(git diff --staged | grep "^-" | cut -b2- | sort) \
           <(git diff --staged | grep "^+" | cut -b2- | sort)
Test: remove comments on plat_sepolicy.cil, replace base_typeattr_*
      to base_typeattr and then compare old and new plat_sepolicy.cil
Change-Id: I5e7d2da4465ab0216de6bacdf03077d37f6ffe12
diff --git a/private/watchdogd.te b/private/watchdogd.te
index 91ece70..509e950 100644
--- a/private/watchdogd.te
+++ b/private/watchdogd.te
@@ -1,3 +1,6 @@
 typeattribute watchdogd coredomain;
 
 init_daemon_domain(watchdogd)
+
+allow watchdogd watchdog_device:chr_file rw_file_perms;
+allow watchdogd kmsg_device:chr_file rw_file_perms;