module loader dead code removal and cleanups v3

Christoph Hellwig
2021-02-02T12:14:58Z

Hi all,

this series removes support for long term unused export types and
cleans up various loose ends in the module loader.

Changes since v2:
- clean up klp_find_object_symbol a bit
- remove the now unused module_assert_mutex helper

Changes since v1:
- move struct symsearch to module.c
- rework drm to not call find_module at all
- allow RCU-sched locking for find_module
- keep find_module as a public API instead of module_loaded
- update a few comments and commit logs