Check R_*_IRELATIVE in x86 reloc_type_class

Check R_*_IRELATIVE in x86 reloc_type_class

elf_{i386|x86_64}_reloc_type_class should return reloc_class_ifunc for
R_386_IRELATIVE/R_X86_64_IRELATIVE relocations.  There is no need to
check symbol type for STN_UNDEF symbol index.

	* elf32-i386.c (elf_i386_reloc_type_class): Check R_386_IRELATIVE.
	Don't check symbol type for STN_UNDEF symbol index.
	* elf64-x86-64.c (elf_x86_64_reloc_type_class): Check
	R_X86_64_IRELATIVE.  Don't check symbol type for STN_UNDEF symbol
	index.