hal_dumpstate: allow writing to bug report files

Bug: 31982882
Test: works with wip bullhead binderized dumpstate implementation
Change-Id: Iae964f49b3c2704688ded8e7366d89ace35a92aa

public/hal_dumpstate.te

@@ -3,3 +3,6 @@ hwbinder_use(hal_dumpstate)
 
 # call into dumpstate process (callbacks)
 binder_call(hal_dumpstate, dumpstate)
+
+# write bug reports in /data/data/com.android.shell/files/bugreports/bugreport
+allow hal_dumpstate shell_data_file:file write;