ddraw/tests: Rename mips to mipmaps

[Henri Verbeet]

On 13 December 2015 at 22:33, André Hentschel <nerv at dawncrow.de> wrote:
> GCC for mips defines mips to 1, thus this file won't build with a mips compiler without this patch
>
I think -std=c90 should help with that, although there may be some
instances of e.g. "inline" and "typeof" we'd need to fix. Still, I
like "mipmaps" better than "mips", even though it's supposed to be
called "mipmap_count".