elf: Renumber local dynamic symbols only if needed

elf: Renumber local dynamic symbols only if needed

Only hppa, ia64 and sparc ELF targets use local dynamic symbols.  But
elf_link_renumber_local_hash_table_dynsyms is always called to renumber
local dynamic symbols even if there is none.  Add has_local_dynsyms to
elf_link_hash_table and set it to true only if there are local dynamic
symbols.  Renumber local dynamic symbols only if there are local dynamic
symbols.

	* elf-bfd.h (elf_link_hash_table): Add has_local_dynsyms.
	* elflink.c (_bfd_elf_link_renumber_dynsyms): Renumber local
	dynamic symbols only if there are local dynamic symbols.
	(_bfd_elf_adjust_dynamic_symbol): Set has_local_dynsyms if
	there are local dynamic symbols.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>