s390: Check UNDEFWEAK_NO_DYNAMIC_RELOC

s390: 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
	* elf32-s390.c (allocate_dynrelocs): Discard dynamic
	relocations if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
	(elf_s390_relocate_section): Don't generate dynamic relocation
	if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
	* elf64-s390.c (allocate_dynrelocs): Discard dynamic
	relocations if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
	(elf_s390_relocate_section): Don't generate dynamic relocation
	if UNDEFWEAK_NO_DYNAMIC_RELOC is true.