firmware: cs_dsp: Add test cases for client_ops == NULL

Add test cases for the client not providing a pointer to a
struct cs_dsp_client_ops. This proves that it is safe for the client
to leave the client_ops pointer at NULL if it does not need to
implement any of the callbacks.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://patch.msgid.link/20251128102132.1575177-3-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: rfvirgil

drivers/firmware/cirrus/test/cs_dsp_test_callbacks.c

@@ -600,6 +600,7 @@ KUNIT_ARRAY_PARAM(cs_dsp_callbacks_ops,
 
 static const struct cs_dsp_callbacks_test_param cs_dsp_no_callbacks_cases[] = {
 	{ .ops =  &cs_dsp_callback_test_empty_client_ops, .case_name = "empty ops" },
+	{ .ops =  NULL, .case_name = "NULL ops" },
 };
 
 KUNIT_ARRAY_PARAM(cs_dsp_no_callbacks,