rs6000_emit_set_long_const tidy

[David Edelsohn]

On Wed, Apr 24, 2013 at 7:04 AM, Alan Modra <amodra@gmail.com> wrote:
> This just removes some unnecessary tests.  It's easy to see that if
> the sign bit isn't set then xor 0x8000 followed by subtract 0x8000
> leaves the value unchanged.  Bootstrapped etc. powerpc-linux.  OK
> for mainline?
>
>         * config/rs6000/rs6000.c (rs6000_emit_set_long_const): Tidy.

This is okay.

Thanks, David