In commit 3b3653c4 we decided not to use bare types; hence do not use
bare type when comparing with interface type to find out if the xfb
variable is an array block.

This fixes dEQP-VK.transform_feedback.* tests.

Fixes: 3b3653c4

 ("nir/spirv: don't use bare types, remove assert in
                     split vars for testing")
CC: Dave Airlie <airlied@redhat.com>
CC: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>