PR ld/22832 on SPARC.

PR ld/22832 on SPARC.

The fix for PR ld/22727 on SPARC passed TRUE as the 'create' argument
in the call to bfd_link_hash_lookup.  It turns out this was a bad idea
because, if the symbol is created at this point, the link will abort
later in elf_link_output_extsym.  This changes the TRUE into a FALSE
and puts an assertion on the result of the call, making it easier to
debug the issue; that's exactly in keeping with what Gold does.

bfd/
	* elfxx-sparc.c (_bfd_sparc_elf_check_relocs) <R_SPARC_TLS_GD_CALL>:
	Pass FALSE instead of TRUE as 'create' argument to bfd_link_hash_lookup
	and assert that the result of the call is not NULL.