Revert x86: Allow undefined _DYNAMIC in static executable

This code is used in non-PIE static executable and static PIE.  It checks
if _DYNAMIC is undefined before using it to compute load address.  But
not all targets can convert access _DYNAMIC via GOT, which needs dynamic
relocation, to PC-relative at link-time.

	* sysdeps/i386/dl-machine.h (elf_machine_load_address): Don't
	allow undefined _DYNAMIC in PIE libc.a.
	* sysdeps/x86_64/dl-machine.h (elf_machine_load_address):
	Likewse.