[Inliner] Don't skip inlining alwaysinline in optnone functions

Previously the NPM inliner would skip all potential inlines in an
optnone function, but alwaysinline callees should be inlined regardless
of optnone.

Fixes inline-optnone.ll under NPM.

Reviewed By: kazu

Differential Revision: https://reviews.llvm.org/D83021