hal_wifi: Allow system_server to access wifi HIDL services

We're going to be using Android framework directly to invoke Wifi HIDL
calls. So, change permissions appropriately.

Bug: 33398154
Test: Verfied that framework is able to make HIDL calls using
go/aog/310610.

Change-Id: I4d0d88961753ad73f3876aec58b26b89486cc02a