objtool: update .gitignore file

With the recent sync with objtool from 4.14.y, the objtool .gitignore
file was forgotten.  Fix that up now to properly handle the change in
where the autogenerated files live.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tools/objtool/.gitignore

-arch/x86/insn/inat-tables.c
+arch/x86/lib/inat-tables.c
 objtool
 fixdep