retire arm64 kernel module linker workaround

[emaste]

Summary

Relocatable linking in aarch64 ld from binutils 2.25.1 does not work. The linker corrupts the references to the external symbols which are defined by other object in the linking set and should therefore lose the GOT entry.

The problem is fixed in later versions of GNU ld and does not exist in the in-tree lld linker that we now use by default for arm64, so the workaround can be removed.

Test Plan

Install on OverDrive 1000 a kernel + modules built with this change, verify modules can be loaded and operate correctly.