[ELF] - Fix R_AARCH64_ADR_GOT_PAGE, R_AARCH64_LD64_GOT_LO12 handling against IFUNC symbols.

This is https://bugs.llvm.org/show_bug.cgi?id=38074.

The issue is that when calling a function, LLD generates a
.got entry that points to the IFUNC resolver function when
instead, it should use the PLT entries properly for
handling the IFUNC.

So we should create a got entry that points to PLT entry,
which itself loads the value from 
.got.plt, relocated with R_*_IRELATIVE to make things work.
Patch do that.

Differential revision: https://reviews.llvm.org/D54314

llvm-svn: 347650