nak: Enable lowering for bitfield manipulation at <32bit sizes

Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35804>

src/nouveau/compiler/nak/api.rs

@@ -124,6 +124,8 @@ fn nir_options(dev: &nv_device_info) -> nir_shader_compiler_options {
     op.lower_flrp64 = true;
     op.lower_fsqrt = dev.sm < 52;
     op.lower_bitfield_extract = dev.sm >= 70;
+    op.lower_bitfield_extract8 = true;
+    op.lower_bitfield_extract16 = true;
     op.lower_bitfield_insert = true;
     op.lower_pack_half_2x16 = true;
     op.lower_pack_unorm_2x16 = true;