PR23123, PowerPC32 ifunc regression
    
    Two of the gcc ifunc tests fail for ppc32, due to my pr22374 fix being
    a little too enthusiastic in trimming PLT entries.  ppc64 doesn't have
    the same failures because ppc64_elf_check_relocs happens to set
    needs_plt for any ifunc reloc.
    
    	PR 23123
    	PR 22374
    	* elf32-ppc.c (ppc_elf_adjust_dynamic_symbol): Don't drop plt
    	relocs for ifuncs.
    	* elf64-ppc.c (ppc64_elf_adjust_dynamic_symbol): Comment fixes.
    
    (cherry picked from commit 04383fd15b3b82d824df9c72e3ade88c43bfb5ac)