nir: only uniforms with dynamically_uniform offset are dynamically_uniform

nir: only uniforms with dynamically_uniform offset are dynamically_uniform

Previously all nir_intrinsic_load_uniform that were used as sources were
considered to be dynamically_uniform but when offsets of load_uniform
are indirect it can not be determined.

This fixes artefacts in Google Maps 3D view in V3D.

Fixes: 886d46b08971 ("nir: Add a function to determine if a source is dynamically uniform")
Reviewed-by: Neil Roberts <nroberts@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5587>