nir: handle load_input_vertex in nir_get_io_offset_src

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6328>
diff --git a/src/compiler/nir/nir_lower_io.c b/src/compiler/nir/nir_lower_io.c
index 58c4597..fd5a713 100644
--- a/src/compiler/nir/nir_lower_io.c
+++ b/src/compiler/nir/nir_lower_io.c
@@ -1553,6 +1553,7 @@
       return &instr->src[0];
    case nir_intrinsic_load_ubo:
    case nir_intrinsic_load_ssbo:
+   case nir_intrinsic_load_input_vertex:
    case nir_intrinsic_load_per_vertex_input:
    case nir_intrinsic_load_per_vertex_output:
    case nir_intrinsic_load_interpolated_input: