Adds GPU sepolicy to support devices with DRM gralloc/rendering

... such as Cuttlefish (Cloud Android virtual device) which has a
DRM virtio-gpu based gralloc and (sometimes) DRM virtio-gpu based
rendering (when forwarding rendering commands to the host machine
with Mesa3D in the guest and virglrenderer on the host).

After this change is submitted, changes such as aosp/1997572 can
be submitted to removed sepolicy that is currently duplicated
across device/google/cuttlefish and device/linaro/dragonboard as
well.

Adds a sysfs_gpu type (existing replicated sysfs_gpu definitions
across several devices are removed in the attached topic). The
uses of `sysfs_gpu:file` comes from Mesa using libdrm's
`drmGetDevices2()` which calls into `drmParsePciDeviceInfo()` to
get vendor id, device id, version etc.

Bug: b/161819018
Test: launch_cvd
Test: launch_cvd --gpu_mode=gfxstream
Change-Id: I4f7d4b0fb90bfeef72f94396ff0c5fe44d53510c
Merged-In: I4f7d4b0fb90bfeef72f94396ff0c5fe44d53510c
diff --git a/private/genfs_contexts b/private/genfs_contexts
index 2f1f84d..1c604fc 100644
--- a/private/genfs_contexts
+++ b/private/genfs_contexts
@@ -123,6 +123,7 @@
 genfscon sysfs /devices/system/cpu u:object_r:sysfs_devices_system_cpu:s0
 genfscon sysfs /class/android_usb                 u:object_r:sysfs_android_usb:s0
 genfscon sysfs /class/extcon                      u:object_r:sysfs_extcon:s0
+genfscon sysfs /class/gpu                         u:object_r:sysfs_gpu:s0
 genfscon sysfs /class/leds                        u:object_r:sysfs_leds:s0
 genfscon sysfs /class/net                         u:object_r:sysfs_net:s0
 genfscon sysfs /class/rfkill/rfkill0/state        u:object_r:sysfs_bluetooth_writable:s0