[ELF] Don't error on R_PPC64_REL24/R_PPC64_REL24_NOTOC referencing...

[ELF] Don't error on R_PPC64_REL24/R_PPC64_REL24_NOTOC referencing __tls_get_addr for missing R_PPC64_TLSGD/R_PPC64_TLSLD

This partially reverts D85994.

In glibc, elf/dl-sym.c calls the raw `__tls_get_addr` by specifying the
tls_index parameter. Such a call does not have a pairing R_PPC64_TLSGD/R_PPC64_TLSLD.
This is legitimate. Since we cannot distinguish the benign case from cases due
to toolchain issues, we have to be permissive.

Acked by Stefan Pintilie