modprobe: add -s/--syslog flag

There is a desire to ensure that modprobe as a service can log to
kmesg to help triage issues, so add support for the -s or --syslog
flag to do so.

Bug: 159424228
Bug: 151950334
Test: use modprobe as a service to load modules, check logs
Change-Id: I884995f364b0fc604861797eb90d7225a372f864
diff --git a/vendor/vendor_modprobe.te b/vendor/vendor_modprobe.te
index 61df9e0..4628ecc 100644
--- a/vendor/vendor_modprobe.te
+++ b/vendor/vendor_modprobe.te
@@ -5,6 +5,7 @@
 
 allow vendor_modprobe proc_modules:file r_file_perms;
 allow vendor_modprobe proc_cmdline:file r_file_perms;
+allow vendor_modprobe kmsg_device:chr_file w_file_perms;
 allow vendor_modprobe self:global_capability_class_set sys_module;
 allow vendor_modprobe kernel:key search;