Remove default impls from clock plugins

This appears to prevent crashes from dynamic loading failures when
building and deploying sysui & wpp from sysui studio instead of building
through soong.

Bug: 279049213
Test: Deployed wpp & sysui from sysui studio
Change-Id: I6225f9529898ef8c6f4953957fb83cf0cd2abda0
2 files changed