freedreno/ir3: don't rely on intr->num_components

freedreno/ir3: don't rely on intr->num_components

It is better to use `nir_intrinsic_dest_components()` which also handles
the case of intrinsics with a fixed number of dest components.

Somehow this starts showing up with a nir_serialize round-trip with
shader-cache.  But we really shouldn't have been relying on
`intr->num_components` directly.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5371>