r600g: get s3tc working on cards with crappy 64/128 bit types.

r600g: get s3tc working on cards with crappy 64/128 bit types.

Some cards don't appear to work correctly with the UNORM type,
so switch to the integer type, however since gallium has no
integer types yet from what I can see we need to do a hack to
workaround it for the blitter.

Signed-off-by: Dave Airlie <airlied@redhat.com>