m68k: 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-m68k.c (elf_m68k_check_relocs): Don't allocate dynamic
	relocations if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
	(elf_m68k_adjust_dynamic_symbol): Don't make symbol dynamic if
	UNDEFWEAK_NO_DYNAMIC_RELOC is true.
	(elf_m68k_relocate_section): Don't generate dynamic relocation
	if UNDEFWEAK_NO_DYNAMIC_RELOC is true.