ia64: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

	PR ld/22269
	* elfnn-ia64.c (elfNN_ia64_check_relocs): Don't allocate
	dynamic relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
	(allocate_fptr): Don't allocate function pointer if
	UNDEFWEAK_NO_DYNAMIC_RELOC is true.
	(allocate_dynrel_entries): Don't allocate dynamic relocation
	if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
	(set_got_entry): Don't set GOT entry if
	UNDEFWEAK_NO_DYNAMIC_RELOC is true.
	(set_pltoff_entry): Don't set PLTOFF entry if
	UNDEFWEAK_NO_DYNAMIC_RELOC is true.
	(elfNN_ia64_relocate_section): Don't install dynamic relocation
	UNDEFWEAK_NO_DYNAMIC_RELOC is true.