Allow adbd access to gpu_device.

Addresses denials seen when attempting to take a screencaputre from ddms:
<5>[ 1232.327360] type=1400 audit(1393354131.695:41): avc:  denied  { read write } for  pid=18487 comm="screencap" name="nvhost-ctrl" dev="tmpfs" ino=4035 scontext=u:r:adbd:s0 tcontext=u:object_r:gpu_device:s0 tclass=chr_file

Bug: 13188914
Change-Id: I758e4f87ab024035604d47eebae7f89f21ea1e3e

adbd.te

@@ -50,6 +50,8 @@ unix_socket_connect(adbd, vold, vold)
 # XXX Run screencap in a separate domain?
 binder_use(adbd)
 binder_call(adbd, surfaceflinger)
+# b/13188914
+allow adbd gpu_device:chr_file rw_file_perms;
 
 # Read /data/misc/adb/adb_keys.
 allow adbd adb_keys_file:dir search;