Currently the following 3 relocation types do not trigger the creation
of a canonical PLT (which changes STT_GNU_IFUNC to STT_FUNC and
redirects all references):
- GOT-generating (needsGot)
- PLT-generating (needsPlt)
- R_ABS with 0 addend in a writable location. This is used for for ifunc function pointers in writable sections such as .data and .toc.
This patch deletes case 3) to simplify the R_*_IRELATIVE generating
logic added in D57371. Other advantages:
- It is guaranteed no more than 1 R_*_IRELATIVE is created for an ifunc.
- PPC64: no need to special case ifunc in toc-indirect to toc-relative relaxation. See D65755