Add sepolicy for rtc-test driver

When updating the kernel for cuttlefish, new sepolicy denials are seen:

avc: denied { read } for comm="system_server" name="hctosys" dev="sysfs"
  ino=9707 scontext=u:r:system_server:s0 tcontext=u:object_r:sysfs:s0
  tclass=file permissive=1
avc: denied { open } for comm="system_server"
  path="/sys/devices/platform/rtc-test.0/rtc/rtc0/hctosys" dev="sysfs"
  ino=9707 scontext=u:r:system_server:s0 tcontext=u:object_r:sysfs:s0
  tclass=file permissive=1
avc: denied { getattr } for comm="system_server"
  path="/sys/devices/platform/rtc-test.0/rtc/rtc0/hctosys" dev="sysfs"
  ino=9707 scontext=u:r:system_server:s0 tcontext=u:object_r:sysfs:s0
  tclass=file permissive=1

Although system_server is in "permissive" mode right now, this may not
be the case forever, so fix these warnings.

Bug: 127373130
Change-Id: Ic4e98b989db3a4dd27f4f9a7f083c14503785a42
Signed-off-by: Alistair Delva <adelva@google.com>
diff --git a/shared/sepolicy/vendor/genfs_contexts b/shared/sepolicy/vendor/genfs_contexts
index c8974cd..b894b1b 100644
--- a/shared/sepolicy/vendor/genfs_contexts
+++ b/shared/sepolicy/vendor/genfs_contexts
@@ -1,4 +1,5 @@
-genfscon sysfs /devices/pnp0/00:00/rtc  u:object_r:sysfs_rtc:s0
+genfscon sysfs /devices/pnp0/00:00/rtc  u:object_r:sysfs_rtc:s0 # qemu virtual rtc
+genfscon sysfs /devices/platform/rtc-test.0/rtc  u:object_r:sysfs_rtc:s0 # crosvm has no rtc, use kernel test driver
 genfscon sysfs /devices/pci0000:00/0000:00:07.0/virtio5/net u:object_r:sysfs_net:s0 # (new) qemu buried_eth0 & wlan0
 genfscon sysfs /devices/pci0000:00/0000:00:08.0/virtio6/net u:object_r:sysfs_net:s0 # (new) qemu rmnet0
 genfscon sysfs /devices/pci0000:00/0000:00:09.0/virtio8/net u:object_r:sysfs_net:s0 # (new) crosvm buried_eth0 & wlan0