MIPS rtld: report missing symbol rather than segfaulting

This is only an interim fix; MIPS should be using the MI code instead,
which does not have this issue.

Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D661

libexec/rtld-elf/mips/reloc.c

@@ -245,7 +245,7 @@ _mips_rtld_bind(Obj_Entry *obj, Elf_Size reloff)
         def = find_symdef(reloff, obj, &defobj, SYMLOOK_IN_PLT, NULL,
 	    NULL);
         if (def == NULL)
-		_rtld_error("bind failed no symbol");
+		rtld_die();
 
         target = (Elf_Addr)(defobj->relocbase + def->st_value);
         dbg("bind now/fixup at %s sym # %jd in %s --> was=%p new=%p",