nir: Fix num_ssbos when lowering atomic counters

nir: Fix num_ssbos when lowering atomic counters

Otherwise it's impossible to know the maximum SSBO index for both
internal TGSI shaders from TTN (which don't have any notion of atomic
counters and no offset) as well as shaders from GLSL.

I fixed everything I could find while grepping for num_ssbos and
num_abos, which hopefully is everything (iris was the only user I could
find that uses it in a meaningful way).

Reviewed-by: Marek Olšák <marek.olsak@amd.com>