bfd: Make bfd.stamp depend on source bfd.texi

Make bfd.stamp depend on source bfd.texi to avoid regenerating
doc/bfd.info for each make run.

	PR binutils/28807
	* Makefile.in: Regenerate.
	* doc/local.mk (%D%/bfd.stamp): Depend on $(srcdir)/%D%/bfd.texi.