Be specific for the GPU domains so that we can detect if userspace ever
passed in an invalid combination, as well as accurately reflect the
known GPU domains when printing state.

Fixes i-g-t/gem_exec_bad_domains

References: https://bugs.freedesktop.org/show_bug.cgi?id=57826Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>