NetBpfLoad: Get logs back

r.android.com/3005052 changed the user id of the bpfloader service to
system, which cut off its access to /dev/kmsg, resulting in its logs
silently being dropped. Give back its access to /dev/kmsg.

See //system/core/init/README.md:

file <path> <type>

Open a file path and pass its fd to the launched process. type must be "r", "w" or "rw". For native executables see libcutils android_get_control_file().

and //system/libbase/logging.cpp's OpenKmsg()

Test: boot sdk_phone64_x86_64, check logs
Change-Id: I65f00545400140983737f3ff92e2c912eebce1fd
diff --git a/netbpfload/netbpfload.mainline.rc b/netbpfload/netbpfload.mainline.rc
index d7202f7..d38a503 100644
--- a/netbpfload/netbpfload.mainline.rc
+++ b/netbpfload/netbpfload.mainline.rc
@@ -10,6 +10,7 @@
     capabilities CHOWN SYS_ADMIN NET_ADMIN
     group system root graphics network_stack net_admin net_bw_acct net_bw_stats net_raw
     user system
+    file /dev/kmsg w
     rlimit memlock 1073741824 1073741824
     oneshot
     reboot_on_failure reboot,bpfloader-failed