turnip: fix cube map array image size calculation

imageSize() expects the last component of the return value to be the
number of layers in the texture array. In the case of cube map array,
it will return a ivec3, with the third component being the number of
layer-faces.

Fixes: dEQP-VK.image.image_size.cube_array.*
Signed-off-by: Samuel Iglesias Gonsálvez's avatarSamuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Eric Anholt's avatarEric Anholt <eric@anholt.net>
Part-of: <mesa/mesa!8087>
parent 8c5c1337
Pipeline #245986 waiting for manual action with stages