i965: Remove brwIsProgramNative

i965: Remove brwIsProgramNative

Originally I just fixed some unused parameter warnings in this
function.  However, Ken pointed out:

    "You could instead remove this driver hook.  If the dd pointer is
    NULL, arbprogram.c will return true.  I think I'd prefer that."

Way, way back in time, I think _mesa_GetProgramivARB had the opposite
behavior.  Given that it works the way it now works, I also prefer
removing the driver hook.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>