Adding 'uhid' permission for bluetooth stack.

This CL is in support of another CL c/2048848, topic
'Refactor hid command in /frameworks/base/cmds'
in internal master. Adding the permissions for bluetooth
devices here to access uhid_node as part of the new 'uhid'
group.

Bug: 34052337
Test: Tested on angler, bluetooth mouse works OK.

Change-Id: I63963984a0a3dccb4fccc64bb6fef4e809e2737e

data/etc/platform.xml

@@ -45,6 +45,7 @@
     <permission name="android.permission.BLUETOOTH_STACK" >
         <group gid="bluetooth" />
         <group gid="wakelock" />
+        <group gid="uhid" />
     </permission>
 
     <permission name="android.permission.NET_TUNNELING" >