DrmHal: remove permission check

Permission check should now be performed in HIDL HALs. The removed app-side
permission check does not accomplish much because any app can communicate
with a Drm HIDL HAL directly.

Bug: 134787536
Test: CastV2SignerTest
Change-Id: I4d90effbc0a265459829c63e843b9a5d16e75359